elesone

The car:
90 IROC Z28 5.0L/5 speed
Previously the car started right away and ran fine till it got warm. Then within 15 mins it starts to surge 650 to 1200 repeating the cycle at the speed of a human breathing (about every 2 secs). Sometime it will not start again till it cooled off a little. Got stuck a couple of times on the road from not starting.
Then one day it just would not start. Just cranks. So knowing it needs air, fuel and spark to run I checked the following. BTW - has brand new dizzy assembly and spark plug wires prior to the problems.

1. Spark at the coil wire.
2. Spark at least at four spark plugs.
3. Both sides injectors are firing.
4. Fuel pressure 35 psi and drops to 20 psi after key off.
5. Pinch return line, pressure 44 psi and holds after key off.
6. Un-pinch and psi drops to zero.
7. Squirt gas in throttle body and engine starts right away and runs till it uses the squirted amount.
8. Had someone crank it while I squirted gas and runs as long as I'm squirting gas. Stops 2 secs after I quit squirting.
9. Installed a Bosch in line fuel pump to the feed line and had 45 psi steady.
10. Crank it over with the Bosch running but still will not start.
11. Squirt gas with the in-line pump running and engine runs till squirt is exhausted.
12. Checked spark plugs for fouled condition. No issues.

So is it false to assume that since the in-line pump pressure provides 45 psi it does not matter if the regulator is weak?

Thank you in advance.

elesone

Hi all. Any chance anyone can help? I read so many similar threads but not one could relate to my problem. Looks like most are fed up of the repeat ability on the same issue.

bigal55

iTrader: (1)

If you are sure you have spark and the engine runs while you squirt gas into the throttle body, chances are you are not getting injector pulses. You state the injectors are being pulsed, I have to ask, how did you check the injector pulses? I went through this same scenario with another member, he hooked up a pressure gauge to his TBI system and thought his pressure was good. After many posts and a lot of work on his part, he discovered his pump was bad and needed to be replaced. Lesson to be learned, be sure when you make measurements or take readings, be sure of your procedure and your findings. Pinch off the return line and see if the engine will start, record the fuel pressure while cranking. HTH!

elesone

bigal55, thanks for the reply. Now I will address your questions.

how did you check the injector pulses?
I used a noid light on 2 injectors per side.

be sure when you make measurements
As I stated in #4 of my post, the pressure was 35 psi while cranking and drops when I let go of the key.

Pinch off the return line and see if the engine will start
As stated in #5, when pinched I got 44 psi, but forgot to mention I tried to start it while pinched. I even squirted gas while pinched and ran for 2 - 3 secs. Unpinch the line and drops to zero.

If the injectors were not pulsing my guess would be, it will not fire with the squirt. But again that's why I'm asking, I'm not an expert.
Thanks again.

bigal55

iTrader: (1)

The engine need fuel, air and spark to run. You have air and spark (proven by the fact the engine fires when you squirt gas into the throttle body), so that leaves the fuel out of the equation. Your statement "If the injectors were not pulsing my guess would be, it will not fire with the squirt" is incorrect as squirting the gas into the throttle body bypasses the injectors and provides the needed fuel, thus completing the equation. I would be looking at the fuel system, the fuel pump in particular. The pump being inside the gas tank does not make it easy, but the pumps in these cars could be 30 years old. There is a small hose that connects the pump to the outlet of the gas tank (pulsator as it is referred to) that is notorious for failure. Unfortunately, the gas tank needs to be dropped in order to access the pump/sending unit and check/replace the unit. As I said earlier, be sure of your testing procedure and check your findings carefully to avoid any undue work involved in removing the tank. With 45 psi, I would think the engine would start or at least try to fire as long as the injectors are firing. You could remove the coil wire so the engine gets no spark and crank it for about 30 seconds. Immediately remove a couple of spark plugs to see if they are "wet" with fuel. This will at least tell you if the engine is indeed getting fuel from the injectors. I am still leaning toward the fuel pump, but the pressures you are reading kind of lead me away from that diagnosis. This is why you need to be sure your injectors are firing and delivering fuel to the engine. HTH!

elesone

bigal55:
You're right about the injectors not in the equation when squirting gas. My mistake in thinking that. I realize now that the injectors are electrically charged to squirt the gas in the intake manifold.
The in-tank pump provides 35 psi at the rail. I also added another in-line fuel pump that provides 44 psi at the rails. I installed a light noid on four injectors (2 per side) to ensure the injectors are firing. Still it won't start. But if I squirt gas with both pumps supplying 44 psi, it will start immediately. No rich smell at all.
Let's assume the pulsator failed or fell off. I should not get pressure..RIGHT?

Assumption:
The rail sees 44 psi, therefore the injectors see 44 psi. Doesn't that eliminate the pump(s). Remember I said the car ran and one morning it would not start. What are the chances ALL injectors got plugged overnight? I will do what you suggested (You could remove the coil wire so the engine gets no spark and crank it for about 30 seconds. Immediately remove a couple of spark plugs to see if they are "wet" with fuel.)
Thanks.

bigal55

iTrader: (1)

The in-tank fuel pump may provide pressure when all the injectors are not firing (key on engine off or not cranking) but may not be able to keep up with the volume when the injectors start pulsing. If this were the case, I would expect to see the pressure drop when cranking (injectors firing). Obviously, you are enriching the mixture when you squirt the gas into the throttle body which allows the engine to fire. You need to see what is limiting your fuel into the engine. Get a DVOM (digital volt ohm meter) and measure the resistance of your injectors (all of them) to see that they are in the 12 - 16 ohm range. Could be a bad injector. At this point, you know it is fuel related so you need to concentrate in that area. How did those plugs look?

mcgarnicle

iTrader: (14)

Sounds like a bad fuel pressure regulator.



The inline pump that you installed, is it wired to a wire that is hot while cranking?


Is the fuel pressure maintaining 44psi during cranking?


Personally I would want either a good in-tank pump or an in-line tank, but not both. Especially if the in-tank pump is dying.

elesone

mcgarnicle - thanks for joining in.
With the in-line fuel pump hooked up directly to the battery which runs constantly and the fuel pressure is a steady 44 psi.

bigal55 -
cranking the engine for 30 secs does not contaminate the plugs. they are dull sooty black no shine or sign of gas fouled plugs. I checked them before and after the 30 secs crank.
Injector ohms are as follows
(1.3.5.7) 16.0, 15.9, 16.0, 10.0
(2,4,6,8) 16.2, 15.6, 15.8, 16.3
The bold numbers are out of the 12 - 16 range.

I tried something else. Noticing the column is loose and the key cylinder moves in/out about 1/8" I put the key in and the alarm goes of and on at will, sometimes no alarm at all. I also found a bypass for the vats which incorporate the spare chip key soldered to 2 wires. That could be the reason why the noid lights worked (just lucky) but attempts to fire while cranking. So I turned the key on engine off, pulled on the column sideways till I got a constant key alarm and within 10 secs it started and ran. I let go of the column and it ran for about 30 secs, then it quit, probably from the vibrations.
I repeated the forcing of the column sideways to start it but this time as I let go of the column it quit. Obviously vats is the issue.
Your thoughts.

bigal55

iTrader: (1)

It sounds like you found the culprit. VATS will not allow the injectors to fire and agrees with your finding of "dry" plugs after cranking with no spark. The mystery is the flashing noid light you had on both banks of injectors. Check the wiring from the column to the VATS module, it sounds like it has a break somewhere. The resistors are ok to bypass the VATS system, if that is what ok with you, but they need to be secure in their connection to the wiring. Correct the wiring fault and everything should be good.


Just re-read your last post and realized you have the spare key soldered to the VATS wires. De-solder the key and use resistors instead. Use your DVOM to read the resistance of the key and get a resistor(s) that matches your ohm reading.

elesone

Thanks bigal55.
The working noid light could be coincidental at that particular time. I can put the key in the cylinder and get no buzz, wiggle the column and the buzz gets intermittent. Sometimes it starts and most of the time it does not. But you're right, have to disassemble the soldered key from the crap it has around it and do the resistor method. Just one thing, this soldered key is NOT inside the column but hanging out and tucked under the dash. When I pull the soldered key from under the dash, it hangs and almost touches the floor. The mystery still haunts me, what is acting up when the column or the key cylinder are wiggled while the soldered key is hanging?

You mentioned to "Check the wiring from the column to the VATS module". Are there other wires besides the 2 going to the cylinder? I guess I'll find out when I take the column apart. I did this a couple of times before.
Thanks.

bigal55

iTrader: (1)

No other wires, just the 2 that are soldered to the key. Is your starter relay jumpered out? The reason I ask is, the VATS system, or ECM to be exact, will not energize the starter relay if it has any issues. Again, seems weird it will crank but not fire the injectors. Usually only need to apply the resistor bypass to skirt the VATS system. Wondering if the PO had problems and did the starter relay jumper thinking maybe the relay was bad then discovered the car still would not start and then went on to do the resistor bypass (used a second key instead of resistors). Sounds like the ignition switch could have been the problem all along. Nothing wrong with leaving the starter relay jumered out as its only function was for VATS anyway and that has since been bypassed. Checks those wires to the VATS module and solder in some real resistors. GL!

elesone

Don't know if the starter relay is jumper-ed out. Once I disassemble the column coz it's really loose (4 torx screws), I will trace the wires to the module looking for other surprises.
I'm trying to find an article I read somewhere that stated one malfunction deactivated the starter and the injectors, and a different malfunction deactivated the injectors ONLY. In the meantime I'll keep tracing wires.

bigal55

iTrader: (1)

Quote "The mystery still haunts me, what is acting up when the column or the key cylinder are wiggled while the soldered key is hanging?"


Doesn't the ignition switch reside at the base of the column with a linkage rod to the key cylinder? I don't own a third gen so I can't confirm this but if it is connected via a linkage rod, it could be out of adjustment or the loose column is moving the linkage enough to turn the ignition off? Just a thought.

greenyone

iTrader: (1)

Yes. And if I remember correctly, the left side pivot pin on the tilt columns also serves as a guide for the slide assembly that the rod is connected to. If that pivot pin is loose/worn it could cause the whole shebang to have excessive wobble in there and not move the linkage rod properly when you turn the key/lock-cylinder.

Raysir

So what's the solution??? I have a 49 Chev truck with an 85 Vette TPI wired to MAP of a 91 Vette. I starts and runs great. Quit once and wouldn't restart til it cooled down. Had spark and noid on injectors. I can get it to do it in my garage if I get it hot, wait about 10 minutes and then it cranks and cranks. Maybe one time acts like it'll fire then cranks and no start. Then I can spray fuel , 3 or 4 squirts of fuel from a spray bottle into the intake and it fires right up. The PROM has been set for EGR and VATS delete for a streetrod and the 9th injector cold start deleted. I have a 30GPH inline fuel pump on it and it maintains 41 at idle even when shut off for quite a while. If I bleed off the fuel rail it acts like it's boiling and bubbles like aerating. I just ordered a different pump that puts out 80 GPH and 100psi and plan to get rid of metal hoses for rubber. Sounds like quite a few guys have this problem...we need a solution? You have any? I'll post what happens next week.

mcgarnicle

iTrader: (14)

How are your fuel lines ran? Are you using a return line setup? Your issue kind of sounds like vapor lock. The ICM can also cause similar symptoms but usually wouldn't fire by spraying fuel in the intake.
You can also ohm check your injectors cold and then hot when your symptoms are happening. Should be between 12-16. Any out of that range in either hot or cold needs to be replaced.
Same thing with fuel pressure, check when cold and when hot


Also your symptoms do not sound similar to the OP's question, you may want to start your own thread in maybe the tech/general forum.

southbay08

Sounds like you might have an injector problem. Since you are saying that you have problems when the car is hot and then it's ok when it cools down... check the resistance on the injectors when they are both hot and cold. The injectors from about 1985-1992 or 1993 are very prone to coil failure...especially when they are hot....
Keep us posted

elesone

Raysir - I have a 91 IROC SD set up in my 36 Chev which runs flawless. The "No Start" issue is in a Camaro that initially started and ran but it shut off from 5 - 20 minutes. So it's the same problem as you have. But I will not address that "stall" condition till I get this "No start" fixed. But then I will start a new thread if needed. As you should and suggested by mcgarnicle.
Right now I'm half way in tearing the column apart to fix a wobble.
Thanks for the replies.

Raysir

"But I will not address that "stall" condition till I get this "No start" fixed. But then I will start a new thread if needed. As you should and suggested by mcgarnicle.
Right now I'm half way in tearing the column apart to fix a wobble."

elesone, I hope you don't take it as hijacking a post...not intended for sure. I only posted to try and help each other out.

Fixed a lot of loose columns in my life.. those pesky attach bolts.

I thought you said your Iroc fired and started with a squirt of fuel and had injector pulse. Your post got me to spray fuel and it worked.
I'm in the process of putting on a higher flow fuel pump and changing out some fittings to be sure there's no restricted flow back to the tank. I never took the fuel pressure gauge off the rail all the time I was testing and maintained 41 psi at idle. What I noticed, after it got hot, and putting in clear tubing to the pressure gauge that when I released the pressure it was foamy fuel air bubble like it was boiling. The flow on my inline pump is rated at 30 gph so I'm going to try a 100 gph for flow and maybe get cooler fuel. This build only has 2700 miles on it and all new injectors, dist, 3 different modules, Hytech coil. But never thought to spray fuel since I had pressure... but it was AIR pressure. Your post helped me see what's going on. Hope mine helps you.

alan91z28

i second this from the description of your issue, check your injector's coil resistance

i had this exact problem on my 91 z28 vert that only has 7000 miles on it... in the end i had 3 bad injectors... once replaced i didn't have any start issues.

i did also later replace the ECM as i believe the injectors had also damaged the firing circuit as i would still get cut-outs at high RPM / WOT. after replacing the ECM this problem was then corrected as well

elesone

Raysir - No problem, did not take it as a hijack. Reason was, one time I read a solution in the middle of a thread that started out with a different issue and when I tried to find it I couldn't. So sticking to the same problem within the thread helps during a search, especially if the heading includes the problem description.
I don't know if the loose column is the solution, but it was the only thing that came close to starting the car. Not every time but it's hope. I'll know by the week end.
As far as my injectors ohms, as I wrote in post #9, they vary from 10 to 16.3. No one made comments, so I assume they are acceptable. The 10 ohms one concerns me. How can resistance decrease? These are all originals with 120k miles.
Again, thanks for the input.

southbay08

Hey sorry, didn't see your post. That is not acceptable. They should all be consistent. The one that is reading 10ohms has a failing coil. They should all be around 16ohm or so

elesone

southbay08 - thanks for chiming in. So "16ohm or so" only makes the 10 ohm unacceptable. One weak injector should not prevent the engine from starting. I ran engines before with a light noid in place of the injector. Prior to the "No start" the car started and ran fine for about 15 mins then shutting off.

bigal55

iTrader: (1)

There are a few factors that will change a reading with a DVOM. If there is corrosion on the terminals, you may not get an accurate reading. An injector with a low resistance can load down the drivers and prevent the other injectors from firing as they are all driven in parallel from 1 or 2 drivers (batch fire). I don't believe this is your problem as wiggling the column makes a decided difference in if the engine will start or not. That being said, at 120K miles, it is probably a good idea to replace the injectors anyway. To answer your question on how can heat make the resistance decrease, as the heat builds within the coil, it will expand and then contract when cool again. Although this expansion and contraction is very minimal, it is enough to actually rub the coils and chafe them enough over time that they short to each other internally. Let us know how you make out with the column. GL!

vinny R

The one injector being bad and the lack of consistency is probably the cause of it surging and stalling. They won't prevent it from starting but it sure will prevent it from running properly. With numbers like you have once you get the VATS taken care of it sounds like a set of injectors should be in your future.

elesone

UPDATE, well kinda. I had a few issues tearing the column apart so I decided to remove it from the vehicle to finish the tear down. What I found were a bad ignition switch at the bottom of the column and very warn pivot holes. The holes are oval which prevented the rod going to the ignition switch to fully engage the switch relative to the key lock. Also the switch does not spring back from the cranking position. Can't find parts for the column for I do not know what other columns share the same parts. I have other columns namely Fiero and Olds and none fit. I checked with bone yards here in Ontario, Canada and their listings do not show cars at the yards. Can't even find complete columns without giving up the 1st. born. So the project is on hold till I find parts.
IDEA - what do you think if I just plug in a good ignition switch to the harness and using the vats by-pass while sliding the good switch to start the car? Will it work?

greenyone

iTrader: (1)

I can't say for sure on a 90. But the 91 and 92 air bag columns have pretty much the same internals as a 4th gen column. I pulled a 4th gen from a pic-a-part ($50) that didn't have the pivot pin wobble and used the upper pivot assembly and bearings in my 1991 column. The upper/outer assembly is usually the one that the pivot holes get stretched on, so I didn't need to use the lower/inner assembly. I just re-used the one from my 91 after removing the 4 bolts that hold it on and re-installing them after a cleaning and lock-tight applied. By the looks of it, even the ignition switch at the base of the 4th gen column appears to be identical to the 1991 switch.

greenyone

iTrader: (1)

I don't see any reason why that won't work though. The key just moves the switch via linkage. So it should work by just pushing the linkage.

elesone

greenyone - thanks for chiming in. I'm gonna look into the 4th gen. I need both halves of the tilt supports. In my column the left pin is loose in the upper half by .0015 which crawled out tilting the opposite wearing the right side oval of the lower half. Both halves are toast. Do you know if the lower (with the 4 bolts) is also interchangeable?
Thanks again.

greenyone

iTrader: (1)

It should be. Actually I think the tilt assembly as a whole (upper and lower) is pretty much the same on all GM cars of that era with the tilt wheel. Best to go to a yard and wiggle a bunch of steering wheels on parts cars to find a good one though. I know Hawks and some other vendors sell complete used columns for our cars, but I went the bone-yard route not only to save money, but I also wanted to wiggle a bunch of wheels to make sure I was getting a tight one that didn't already have a loose pivot assembly.

elesone

quote - "Actually I think the tilt assembly as a whole (upper and lower) is pretty much the same on all GM cars of that era with the tilt wheel"
That's what I thought. I have a 92 Olds Cutlas column that I tore down to find neither half comes close. Totally different. I'll check the 4th gen availability. Hate to buy one other than 4th gen and find the parts don't fit.

GCrites80s

Your Fiero and Olds columns might be different from not having airbags and being from a mid-engine and FWD car respectively.

elesone

Well everyone, I tried the ignition switch trick (with the column on the work bench) but still no start. I could tell it's trying to fire, but no luck. So now I have to check the fuel system over again, before I replace the fuel pressure regulator. Stay tuned (no pun intended).

bigal55

iTrader: (1)

Hey elesone, sorry I haven't been here for a while. Been in the woods with no computer for the past week (literally in the woods, haha!). Anyway, as for your ignition switch problem, the contacts in your original switch may have gotten burned up or carbon tracked due to the linkage rod not fully engaging or allowing full return to run position after cranking. Did you correct the VATS situation by soldering resistors into the harness as that still may be some of your problem. You have the noid light so may as well test the injectors for pulse from the ECM and try eliminate that as a gremlin. Let us know what you find. GL!

elesone

bigal55 - NP, you did not miss anything. This is a slow process. I'll bet no phone, no email felt good. Just now you have to catch up.
Anyway, I used a known good ignition switch coz I suspected the old switch anyway. The vats issue is definitely verified to work as expected, with the resisters in place. The noid light showed injectors are firing (2/side). So now I started the fuel system check over again in case I missed something.
Using the f/p test lead jumper-ed to the bat 12v, it registers 28 psi. Remove 12v and drops to 20 psi within 3 mins., 10 psi within 10 mins. Pinching the return line produces the exact results, no change up or down. I then used a turkey baster to squirt gas in the hose for the brake booster. The car started right away and ran till the squirted gas was used up. Is my assumption of the pump gone south correct? I will attempt to hook up an in-line fuel pump and try that again. Last time I did that it still would no start.

bigal55

iTrader: (1)

I would check the fuel pressure regulator first. Pinch the return line that goes back to the tank and check that pressure again. With the line pinched off, does the car start? If you still have low pressure, check your in-line filter (I think you said you replaced the filter but check again just to be sure). There is a small hose between the pump and the outlet from the tank (internal an part of the pump/sending unit), some call it a pulsator. It's purpose is to prevent large pulses or pressure spikes in the system. If this hose is split or has a hole in it, it will not allow full pressure from the pump to reach the injectors. If this is the case, you will need to drop the tank anyway and may as well replace the pump to prevent future problems. I went through this same scenario with another member, although his car was TBI, but the symptoms were the same. I'll see if I can find a link to the tread, it is long but the OP linked some videos and pictures of how he dropped the tank without too much trouble. Get that car running, the summers are short enough here in the north! GL!https://www.thirdgen.org/forums/dfi-...aken-when.html


Here's the link:

elesone

OK - To remind every one, the steering column is out of the car and only using the ignition switch. I hooked up the in-line pump to the feed line and wired it up directly to the battery. Got 48 psi with the ign. sw. OFF.
Using the ign sw I cranked it over a couple of times and the engine tried to start. Squirted a teaspoon of gas down the booster hose and started and stayed running for 8 mins then shut off.
While it was running the pressure was 38 psi steady. After it stalled the pressure went back up to 48 psi, then I disconnected the in-line pump and within 15 secs. the pressure went to 10 psi.
I attached 3 pics of the in-line pump setup, pressure w/key off, and pressure with engine running.

elesone

bigal55 - in post #36 I did state that pinching the return line made no difference with the stock pump. By now you already read my post #38 to give you an idea. I know I'm surprised with the out come.

elesone

I can start it with the in-line pump, maintain 38 psi, but shuts off from 1 to 10 mins.
................

bigal55

iTrader: (1)

After the 1 to 10 minute running, does the engine restart? Restart with a squirt of fuel? Are you still getting spark? If no spark, could be the ICM getting hot and shutting down. It sounds as if there may be more than 1 problem, the fuel pump and maybe an ignition problem (not the ignition switch but the primary ignition circuit). Let us know. GL!

elesone

After each time it stalls, I can restart it just don't know when it will stall. It ran as long as 15 mins. No squirt required. It has a completely new loaded distributor.

elesone

I guess this tread is considered solved with the in-tank fuel pump getting weaker to the point where it couldn't provide over 28 psi. Putting an in-line fuel pump proved the in-tank pump was toast. Too many people replace the in-tank pump and end up not being the problem. That's an expensive lesson.

Special thanks go to all that replied and stood by me. Very much appreciated.

mcgarnicle

iTrader: (14)

What did you do then? New in tank pump?

elesone

Not yet. The column is still out waiting for another column or donor column. But yes, a new in-tank pump is inevitable. Already I went to move the car and it did not start. Dummy forgot to connect the in-line pump to the battery.

bigal55

iTrader: (1)

You need to drop the tank and check that pump and specifically the pulsator (hose). You are still waiting on the column to replace so no progress there. As you said, it's a slow process, so let us know. GL!

elesone

Ya, looks like I have to look for a 4th gen column to swap parts. Good 3rd gen columns are hard to find at a decent price. Need the column to move the car to drop the tank. I will report back when it's complete. It may become a winter project.
Thanks.

elesone

Column update - The upper and lower tilt supports from the 4th gen will interchange. Other parts have slight differences like the turn signal wires have different wire colors, the turn cancel springs and the part they fit in are different but will fit as a sub-assembly, the column is 2" longer on the 4th gen. All in all the parts are interchangeable. Lock cylinder is the same including the passkey wires.

elesone

Pump is changed and car is running fine. Thanks for chiming in.

bigal55

iTrader: (1)

Great to hear you got it running! Was the hose on the pump broken or split? How's that column coming? Keep up the good work!