tarheel

Hey guys, i'm trying to restore a 1986 Z28. Totally stock. The car tries to start, but just will not catch and run. It has a good strong cranking sound,but just will not start.
I removed fuel line and it does get fuel. It las new air filter and fuel filter.

Is there something i'm missing? Not sure if choke works correctly and i think the timing is off.

Car does continue to run after i turn igintion off.

lukn4trbl

Timing will get you always!

Do you know how to find TDC for the #1 piston? If you are 100% sure the
balancer and timing tab are phased correctly, you can use the scribe mark.
If not, it's gets a little tricky.

Once the scribe is lined up on the balancer, mark the #1 plug post on the
base of the distributor.

Remove the cap from the distributor.

Note the position of the rotor vs. the mark on the base.

Rotate the distributor base CCW so the mark appears just before the rotor.
(approx. 5 mechanical degrees)

Lock down the distributor base.

Replace the cap.

If fuel and spark is present, the engine will fire right up.

Failing that, trouble-shoot for spark, fuel pressure, etc.

tarheel

OK...i'll try it.

Problem is..i need the car to start in order to time it.

I don't think the choke is working correctly and the engine continues to run after ignition is off...even backfires a few times.

I backed the idle screw all the way down, but the car still idles high like it is still cold. Runs pretty good overall.
Car has 131k miles...all stock except some of the emission isn't connected.

sofakingdom

iTrader: (1)

Leave the "timing" alone.

Unless someone has already messed with it, it's fine; or at least, it is what it was whenever it was running fine. It doesn't just up and jump itself off into the ozone and create a no-start, all by itself out of the blue. Just doesn't happen. Lots of cars run their entire lives, hundreds of thousands of miles, without it ever being touched. In fact, in lots of cars, you CAN'T change it.

All you will accomplish by messing with it, is yet ONE MORE THING that you'll have to go back and put back the way it belongs after you find and fix the REAL problem, whatever that is. It isn't causing a no-start.

What's REALLY going on here? Does the car start and run, or not?

lukn4trbl

You don't actually need to start the car to set initial. You can do that
with the balancer and timing tab.(especially those with timing tape).

Once it's idling, then you can put a gun on it and tweak it.

If the engine runs-on, check for vacuum leaks and excessive fuel pressure.
Make sure all the ports are plugged, and the gaskets and hoses are not
cracked/loose.

Carb setup may also cause run on. How much of the transfer slot is showing?

Which spark plugs (gap and heat range)?

tarheel

Yeah, i'm kinda rambling...

just bought the car a few weeks ago.

-first, it was hard to start (choke would not close)
-ran fine after someone held choke shut
-always idles high and most of the time runs after it's turned off (backfires some)
-after a few violent backfires....it will not start period.
-plugs look fine (gap is off on a few)
-plug wires look good
-vacuum lines look good - i think
-some emission hoses are missing/taped off
-replaced air/fuel filter

lukn4trbl

I'd have a closer look at those vacuum lines. Tape is not a good seal at all.
I suspect leaks in your case.

Backfires may indicate poor vacuum seal, and/or timing.

Check the rotor/balancer phase as suggested. Adjust accordingly.

sofakingdom

iTrader: (1)

Sounds like nothing whatsoever to do with the "timing". That type of problem almost never is.

Leave that alone and forget about it for the time being.

The immediate problem(s) is(are) that the carb isn't working right. Sounds like the choke isn't coming on like it's supposed to, and then when it does fianlly manage to come partway on, it doesn't pull off like it's supposed to. Likely, nothing more complicated than the accumulated funk of however many years.

Rebuild it. Pay careful attention to all the settings (rich stop, lean stop, IAB valve) as you take it apart, so you can put it back together like it was.

Make sure of course, that it has a good tune-up; new plugs, wires, cap, & rotor. Regular AC Delco plugs are fine. I would suggest these wires here. And of course, replace any fornicated vacuum lines.

lukn4trbl

Although I agree this could be a carb setup/choke issue, to suggest the
symptoms are not related to timing is highly misleading.

This car is a restoration, and nobody has a clue as to whether the distributor
was knocked, moved, etc.

His symptoms are:

- Hard starts
- Backfiring
- Run on
- High Idle RPM

Just a few causes of incorrect ignition timing are:

- poor fuel economy
- sluggish acceleration
** hard starting
** backfiring
** engine run-on

A quick 10 minute check to rule out timing, and you're suggesting to forget about it?

tarheel

i failed to mention the sluggish acceleration. Fuel economy? Dunno --haven't driven it more than 100 miles. (plus fuel gauge is broke)lol

Anyway, i'm don't know enough to rebuild a carb or start removing stuff. I want it completely stock.

I'll check the timing and report back...sure i'll have another issue.

thanks guys,

sofakingdom

iTrader: (1)

Fine....

Just don't change it.

It's not the problem. It wasn't working fine one minute, then moved itself the next. Doesn't happen.

The problem is, the choke sticks; won't close right, won't open right. Pretty simple and straightforward. No use twiddling on the dist like a n00b, and then when the REAL problem is addressed, creating just one more unnecessary piece of damage to undo.

Lucid

iTrader: (4)

I agree with lkn4trbl (looking for trouble? lol)

It sounds like timing related. Yes timing can move itself, a slipping balancer would cause that. It sounds like your timing is way off, and its pretty easy to check. 305 engines are extremely timing sensitive for them to run right.

If you pull the cap check the terminals underneath and make sure the rotor is in good condition.

His posts are pretty spot on what you should do, just go back and reread them.

Also after you have gone through your checks, check to see if the SES light blinks or is flickering when it does run. (Do you have to crank it and floor it to get it to fire?)
If it doesnt and you did Everything else he said, i would lean toward a bad ignition module.

Apeiron

No, it wouldn't.

lukn4trbl

I guess gears don't lash, and timing chains don't stretch either huh Sofa?
Have you ever checked the play between a worn distributor gear and cam
gear? How many engines have you actually built, and tuned to spout off
the 'n00b' comment?

The balancer slip would not change the mechanical timing, but it could
cause someone to incorrectly set the timing....so he's (Lucid) onto something.

If you want to be damn sure, you need a piston stop and a degree wheel
to find TDC and check the alignment of the tab/scribe and then move onto
the distributor.

tarheel

Monday, i went to crank it after a week or so sitting. It was hard to start, but did catch and ran well (high idle). After 5 minutes (still high idle) i drove it to Sears for new rubber.
When i turned the key off, the engine kept running for what seemed like 30 secs. Wife told me it shot flames out of the rear exhaust twice. It was shaking pretty hard and then finally stopped running.
Sears folks called next day and could not get it to start. I towed it home and now have the same issue we're discussed.
Any chance the hard shaking moved the cap and threw the timing off more?
It sounds/feels like it's not getting fuel, but i removed fuel line and fuel does come out in spurts.

sofakingdom

iTrader: (1)

No it cannot. How can a "slipping balancer" cause a distributor housing to rotate in the block? On the contrary, a "slipping balancer" will make the timing light SHOW the wrong thing; so even if the timing IS ACTUALLY right, the timing light user will feel obligated to change it. In other words, take an engine whose "timing" is set right, and send it down the tubes by messing with something that wasn't broke in the first place.No they are not; no more so than any other SBC.Definitely true.

OTOH, "check" is different from "twiddle".

Back in the days of points, timing COULD and regularly DID jump off into the ozone out of the clear blue all by itself. However, since the introduction of inductive-triggered electronic ignition systems almost 35 years ago, this has not been a problem. The parts don't move. The "timing" SIMPLY DOES NOT CHANGE unless somebody changes it. Yet, the Friday night McDonalds monkey-spank "cure-all" for EVERY driveability problem STILL remains, "timing" (when it's not "EGR" ). Why?

We have here, the following symptoms:

Hard to start (spins fine but doesn't quite catch, according to the original poster)
Car has run-on
Backfires sometimes during run-on
Idles high
Sluggish acceleration

This is not "timing". This is a clear-cut and obvious case of a choke stuck partway open.

See my signature for help analyzing the single common cause of several related symptoms. No grasping at straws, no appeals to voodoo or mysticism or "things we don't understand", no "maybe it's this, maybe it's that"; just logic. Straightforward, simple, to the point.

So, my advice to the OP remains, sure, feel free to "check" the timing; it only wastes 10 minutes or whatever; just, DON'T TOUCH IT no matter what it says. If for no other reason, than because the balancer might have slipped, in which case, the indication will be different from the actual "timing", and will lead to making a change that will not be an improvement and instead might very well take it from properly set to erroneously set, and creating further work in undoing the mis-adjustment later. Instead, focus and concentrate on the ONE defect (sticky choke) which easily accounts for all the symptoms at hand.
----------
Oops, forgot...

sofakingdom

iTrader: (1)

No....

The "timing" is not off. Or at least, it is not what's causing the car to act like that. Don't worry about it until you take care of the carb.

The cap doesn't control the "timing", in any case.

You have a carb problem, not a "timing" problem.

Take a look at the choke blade. See if it's partway closed, and if it and its linkage is sticky. Easiest way to do this, is to hold the throttle open a bit with one hand, and move the fast idle cam (large green piece on the pass side of the carb, right front corner, moves up and down); and see if it moves freely. It should be COMPLETELY free to move, with some spring tension on it, but no friction.

Lucid

iTrader: (4)

Pretty much, sorry what I meant to say is that if you have a slipping balancer and someone is trying to time it, it will show way off and if you time it with a light it will run like crap.

To check the timing, I would just take spark plug #1 out, stick a finger or rag or something into the cylinder (last time i used a socket extension that only fit partially into the cylinder) and have someone bump the engine over slowly to Top Dead center on the balancer on the INTAKE stroke. When the piston hits top dead center, your finger will be ejected and you can usually hear the gases being expelled out of the cylinder.

Take the cap off the distributor and verify that the rotor is physically pointing at cylinder #1.

Thats it, you know its timed right and its not much more trouble than other methods.

If someone jacked with the timing before or if its off you will know.

Also whats the history of this car? Did you buy it from someone? If this car threw the timing chain before in its history and sold it to you, it might have a damaged camshaft.

You both might be right, it maybe a carb and a timing problem. They both have to work for the car to run properly.

Instead of being absolute in your answers sofakingdom, you should consider the probability that you are not absolutely right in your judgment and try to consider other people's experience with cars.

sofakingdom

iTrader: (1)

Quite right. I do that every chance I get, and even a few that I don't get.

In the multiple decades that I've been in this business and hobby, there are certain patterns of things that I've seen repeat themselves. Most of them are bad. It's a good idea to avoid these.

Very high on the list, is blaming "timing" for driveability problems. Usually this is interpreted to mean "ignition timing", but people often confuse cam timing (timing chain) with ignition timing, since they're both named "timing".

Yes, it can be off. Yes, someone could have already twiddled it and sent it into the ozone. Yes, it isn't always right. But, unless it's REALLY GROSSLY off, its effects are relatively minor; far less serious than the ones described in this post.

Furthermore, it only has 2 ways it can be off; either excessively advanced, or retarded. Each carries with it a specific set of symptoms. Excessive advance causes hard cranking - the rrrrtt, {pause} rrrrrttt, {pause} rrrrrtttt, kind of that; spark knock; and slightly high idle. In RARE and EXTREME cases, it can cause backfiring into the intake, in engines with very large cams or early intake valve timing (low ICL number). Retarded timing causes sluggish performance, very hot exhaust manifolds, and excessive fuel consumption. In RARE and EXTREME cases, it can cause afterfiring into the exhaust, especially in engines with very large cams or with very late exhaust valve timing (low LSA).

So let's compare the OP's complaints to that list there.

The 2 signature symptoms of excessive advance are the cranking problem, and spark knock. I see no mention of either. Therefore excessive advance can be ruled out.

Retarded timing won't cause backfiring into the intake. Therefore it can be ruled out as well.

Guess what! Using logic and reason, we just eliminated "timing" as the root cause of the symptoms!!

So, looking down there in my sig for a hint about how to approach troubleshooting, what would we do next?

The answer of course is, propose some OTHER explanation besides "timing" (since we've already eliminated it from consideration) that fits some convenient one or another of the symptoms, and see if that possible explanation can ALSO account for other symptoms. Right? And then, if we can come up with a SINGLE explanation that accounts for ALL of the symptoms all at one blow, then it's time to quit thinking any further, and start turning bolts. Eh?

A sticking choke accounts for EVERY SINGLE symptom. Easily, cleanly, neatly, done and over with. That includes high idle, hard starting (but no hard cranking), run-on, sluggish performance, and most importantly,So... if this was YOUR car, sitting in YOUR driveway, what would you do?

Would you discover that the car started and ran right when the choke was manipulated by hand, and based on that knowledge, immediately begin dinking with the "timing"?

I hope you wouldn't. I certainly wouldn't either. And neither should the OP.

The car has a sticking choke. The ignition timing, while it might not be "perfect" whatever that is defined as, IS NOT causing the issues he needs to fix. And unfortunately, no matter how reluctant the OP is to repair the carb, the car is NEVER going to work right, no matter how much the "timing" is wanked on, until such time as the carb is repaired. Carbs are notoriously poor at responding to someone's will, unless it's accompanied by action.

tarheel

anyway, back to the issue.

Here is the latest....i replaced the dist.cap and rotor last night. Bought new plug wires,but they gave me the wrong type. After replacing the cap...nothing changed. I did notice however that the plate the rotor screws down to moves freely....maybe 1/2 inch each way. Should there be free play in this metal mount? I don't know the name of it.
There were two pieces in the box. One obviously was the cap..the other a plastic piece with a metal tab. I assume it is he rotor. Two screws hold it in place. The piece this thing screws down (metal) on is the one with movement.

Also, when i remove the air cleaner. All four barrels are closed. I moved the throttle cable, but didn't notice the choke moving at all. I did check to see the light green electrical cable is connected to the choke.

Can the choke be cleaned without breaking the carb apart?

five7kid

iTrader: (14)

There are 4 sets of "blades" on a stock q-jet: on the bottom of the carb are the "throttle blades", with a set of primaries (the small ones in the front), and a set of secondaries (the huge ones in the back). They are operated directly by the throttle, with the small ones opening first, and the large ones only after you really open the throttle. On the top, there is a "choke butterfly" covering both primaries in the front, and in the back a set of "air valves" over the secondary that open relative to how much air the engine can use.

When cold, the choke butterfly should close when the throttle is opened slightly. There is a mechanism built into the choke stuff that also locks the secondary throttle blades closed until the choke is fully open. After the engine first starts, there is a vacuum diaphragm that pulls the choke butterfly open slightly.

On the passenger side of the carb there is a green weight. With the air cleaner off, engine cold and turned off, try doing these things:
1) Without touching the throttle, push the green weight down. The choke butterfly should open.
2) Open the throttle slightly. The choke butterfly should close and the green weight move up. Does it do that?
3) Hold the throttle open slightly. Push down on the green weight, let it up, push down, etc. while holding the throttle open. Does it move freely, or feel gummy, rough, doesn't move up on its own?
4) Plug the vacuum port the air cleaner vacuum hose goes to. Open the throttle slightly to allow the choke to close, then let off the throttle. Try to start the car. If it starts, does the vacuum diaphragm pull in?
5) After all this fiddling, the car may not start because it's flooded. Hold the throttle wide open and try to start it. DO NOT PUMP THE THROTTLE!

All of this assumes you're getting spark. Yes, the round thing with the metal tab is the rotor. The distributor shaft it screws to may have a little slack on the gears, but 1/2" sounds a little high. But, it shouldn't keep it from starting.

tarheel

good response....i'll try those tonight and report back.

thx

sofakingdom

iTrader: (1)

Yes it is normal for there to be a slight amount of play inthe piece the rotor mounts to. That's the distributor shaft, and it rotates (hence the term "rotor"), and it usually has a small amount of slop. ½" would be ALOT. 1/8" is more normal, although it will usually move quite a bit more if it's also allowed to move up and down. It has a gear that's helical, so the very act of moving it up and down (should be no more than 1/8" of that movement) causes it to rotate slightly.

Part 352 in this blowup is the green (usually) fast-idle cam that five7 and I are both talking about. That, and part 350, are what might be gunked up or even rusted, and making it stick.

jwscab

choke pull-off valve is probably no good. Have replaced a few of them on Q-jets. Possibly the small rubber hose used to connect it. If that is loose or cracked or rotten, you'll have all choke, AND a vacuum leak. All problems associated with the symptoms listed.

depending on how long that carb has been sitting, it might be a wise investment to rebuild the thing.

tarheel

where is the rubber hose? There are some cracked hoses around the carb.

Car has been sitting since 2003.

tarheel

On a side note...the green weight has what looks like a brass tab with 'AD' stamped on it. When the weight goes up, i can take my finger and move the brass tab further up toward the hood. Not far, but still there is movement. Everything feels good...no gummy residue.

tarheel

Need some feedback! See above post

naf

iTrader: (7)

Choke pulloff is #55 on the diagram. To test it, remove the vacuum line to it, push the plunger in and hold your finger over the nipple the vacuum line connected to. The plunger should remain in until you release your finger.

The choke pulloff 'pulls' the choke 'off' slightly once the engine starts running and provides vacuum to the canister.

Have you verified spark?

A spray can of carb cleaner around the choke linkage can't hurt.

Is this a computer controlled carb? Is the M/C solenoid clicking when the key is in 'run'?

tarheel

I do not hear clicking when key is moved forward to 'run'. How do i check the m/c solenoid or adjust it?
oh yeah, i replaced the hoses at the choke pull off and reconnected all emission hoses which had serious leaks.
thx,
Greg

dirtywhiteZ28

The car has been sitting since 2003. Uhhh. I would think that alone would point to a gooood chance that the float is not happy. I don't care what the chemical company's say. Gasoline turns into a viscous, mean, sticky, smelly,kerosene like substance when it sits around. These types of problems are common on motorcycles after just a few months, once the bike gets worn in. A car has a better chance of forcing this stuff through since it uses so much more fuel and air to run. But a cars large carb. isn't going to clean itself out completely. Often on a bike, the float needle will develope a sticky ring around the collar, with out taking it out you won't know for sure. Also the choke blade is not wanting to operate correctly, when left sitting the fuel in the carb may have been seeping through the top plate gasket, this is fine and fairly undetectable when its a light amount and the car is being put through its paces regularly. But let it sit long enough and the stuff can seep onto the throttle shafts,choke linkages,etc., and gum them up, hence spay the moving parts with some carb cleaner and a rag under neath to soak up some of the excess. If you want to check the M/C soliniod with out disassembling the carb see the factory manual five7 has posted it tells you exactly where to probe, and see if the plunger moves freely up and down. Lastly and most unlikely the EFE butterfly in the passenger side exhuast collector has a tendency to fail. It may have been in bad shape before the car sat and now its blocking the exhuast on one side making for one very unhappy backpressure situation in the engine. AND DOUBLE CHECK your fuse block for any blown fuses. An electrical short is a joke , they should be called electrical Longs, and can affect all sorts of wayward stuff.

tarheel

good info...learning alot.

Odd though how the car was always a bit hard to start, but would start and run well. It always idled high like it was in 'cold' mode and now just to stop cranking is weird to me.

I did notice some burned wires..they are connected in a plastic housing and mounted to a bracket to the firewall just behind the EGR. I think they are A/C wires...not sure, but i think they were burned before i got the car...dunno though. Any chance these are causing a problem?

Gonna try again today..i put new Radial T/A's on it and it's killing me not to drive into some curves!

dirtywhiteZ28

This may not be in the right direction, but check the EFE, make sure the blade is operating properly. My '84 sat for a number of years, and the butterfly litteraly rusted off the shaft and fell to the bottom of the factory exhuast connector. Sometimes it was blocking the pipe and revving the car or moving it would joustle it around, out of the way. It was weird. When it was in the way, it created enough back pressure to effect the carb in some funny ways. It also created a lot of heat on that side of the firewall. Enough to discolor some of the surounding wires, but they were o.k.. Back before I layed the car up, the EFE would squeake taking off from stop lights, sometimes when I made hard accelerations on the highway too. It is easy to check if the shaft is responding by pulling the vacumm lead off and apply suction by mouth, just don't suck any dirt into your lungs, it won't take to much pressure to get it move the soleniod.This is going to be a process of elimination, one system at a time.

Bane

wow, great thread guys, lots of information for those of us who have this problem. I pretty much have the same problem (minus the backfiring and any knock). For me, some wires fell on the headers and got melted together, so i rewired them and rerouted them to someplace safe, checked all my fuses (cause who knows, maybe one of them burnt out) And than started the car up. My car does the exact same thing as yours (non CCC though) and just recently (last year) had the carb rebuilt. So i'm assuming that my electric choke is broken and needing to be replaced. Thing is, this choke housing is no longer produced by GM, so finding a new one might be tricky. Any suggestions?

dirtywhiteZ28

I recently got a M/C soleniod kit, and thottle shaft rebush kit from Carbsunlimited.com .The price was resonable and they shipped the same day, and e-mailed me the tracking #'s to prove it. They seem to have most of the factory replacement parts for a wide range of GM carbs. I don't want to come off like an ad guy, but I was pretty happy.

naf

iTrader: (7)

If the MC solenoid is not clicking it could be fubar or hung up inside the carb. This, in and of itself, should not cause a no start but may cause, or contribute to, some of your other issues.

Did you verify that the choke pulloff WORKS? Have you verified spark? Fuel in carb throat?

A carb re-build is likely in your future, but I'd get this immediate problem sorted out-at least get it to start and run- before dickering with anything else yet.

Work the throttle by hand and make sure it's squirting fuel in the carb.

Have a friend crank it over while you hold (with insulated pliers) a plug wire an 1/8 inch from a ground (block or heads) to verify spark.

tarheel

i am getting fuel to carb....choke pulloff seems to work...

have not verified spark. I'll use a pair of pliers and check it.

any chance i threw a timing chain during the 'continue to run/backfire' episode?

TreeFiddy

Toasted ignition module?

five7kid

iTrader: (14)

"Throw" a timing chain? No.

Break a chain, or break a gear and skip a tooth, possible. If the chain broke, it would crank very funny (no compression, which isn't what you indicated). If it skipped a tooth, it would probably start but run horribly.

tarheel

the latest....even though i saw fuel spray in a cup (few days ago) it wasn't much so I asked the wife to start the car yesterday and saw NO fuel in the carb. I added a few gallons just to make sure there was fuel.

So, i'm leaning to a faulty fuel pump. Advance auto has a pump for $19. I'll change it today and report back.

naf

iTrader: (7)

Pour a little bit of fuel directly into the carb and try to start it. Couple tablespoons worth should do it.

Don't swap the pump out yet. Could be clogged/improperly installed filter, etc.

tarheel

I tend to believe the pump is clogged. I just don't want this pump to clog when going down the road.

For $19, it's good insurance....thinking the years of sitting got the pump gummed/clogged up.

Lucid

iTrader: (4)

I was going to say open the secondaries by hand with the throttle lever and pour a swig of gas directly into the engine but NAF beat me to it.

When these cars sit awhile, it takes a long time to pump up the pressure enough with the throttle pedal to get it to go.

Apeiron

The pedal has nothing to do with "pumping up" the pressure.

tarheel

After replacing the fuel pump and the two fuel rubber lines i got good results.

I poured gas into the carb and after some attempts the car started and idled very high (2400). I drove the car up/down the road and had decent power. Idle dropped lower.

I returned and found a loose ground, made it snug and started the car and it cranked immediately. Only this time it idles perfect (700) or so. Engine sounds great!

However, when i took it up the road, this time there was no power. Engine idles great and revs good, but when the pedal is pressed, the power is not there. I still suspect the timing is way off so i'll start with that.

Any other suggestions?

thanks for everyone's suggestions. I've learned alot and it cranks and idles perfect so i'm ALMOST there.

Lucid

iTrader: (4)

Is it your job as moderator to correct me?

naf

iTrader: (7)

No, not like paid or anything. He voluntarily comes around and helps out by clearing up a little mis-information now and again

You got it running. Good Deal. Is the Mixture Control Solenoid (MCS) clicking? What ground wire did you reconnect?

tarheel

I hear the clicking (i think)...i'll confirm tonight. Defintely hear a buzzing sound when turn the key from run to start. Once engine starts the buzzing is gone. I don't remember that from my other z's.

The loose ground ran from battery to bracket which holds the alternator. It was loose and wouldn't turn over so i think it was a new problem.

Engine runs great though...and i mean great!

naf

iTrader: (7)

The MCS should be clicking inside the carb. With the key in run and the motor not yet started it should click for about a minute before the ecm turns it off (because it notices that the motor hasn't started).