I have a challenge for you guys....

I am presently on my third third-gen. This car is a 1988 Formula with LO3 and 700R4. The car has about 100K miles on it and aside from Flowmaster , K&N etc is in very original stock configuration.

Let me start by saying that this board has been a very valuable resource for me. I have spent hours searching and reading posts but still my troubles persist...

Around Thanksgiving the car refused to start one afternoon, I had driven it on my lunch break and it ran fine.....

Coil looked really ugly so I replaced it and the car fired right up. Brilliant, I thought. Ran for a week or so the quit again.(failed to restart- ran fine to that point)

I decided that the ignition module must be bad so I changed it out. I also added new plugs/wires cap/bug for good measure. Car ran for maybe a week or so and quit (failed to restart) one afternoon at my daughter's school.

Changed module again. Car ran again. Quit later that evening. (failed to restart)

I determined that the wires on the pick-up coil on my distributor were in bad shape, figured they were shorting out and blowing up my modules (still can't explain why the coil replacement worked the first time) so I bought a new pick up coil. I buggered up my old distributor trying to change the coil so I bought a new distributor from AutoZone which came with yet another new module. Put it in... Car fired right up and ran good for a week or so. Failed to start again at my work - 15 miles from home and I am loosing my sense of humor.

Drug it home....assumed module was bad again...this time the new distributor module had a sticker on it that said the warranty was void if removed so I figured I' d play it their way...pulled the new distributor out and swapped it for another one. No go. Put in a new coil -just in case. Still no go. Pulled the module off the new distributor put one of my "old" new ones on. No go. Had the "old new module tested...failed on dwell, so they gave me another new module...now here's where things get weird.

I have spark. I can see it and It's strong too...don't ask me how I know. I rolled the motor to #1 TDC (I'm getting good at this now ) verified with the compression puff and timing mark (so I know I'm not on #6). Lined up the dist. to the notch closest to #1 on the cap. Tried to start car...nothing. Nothing even after rotating the distributor +/- 60 degrees in each direction.

Yes, the wires are in the correct firing order and Yes, I have fuel flow visible at the injectors and a strong fuel odor after cranking for awhile. I'm thinking even if I had a fuel delivery problem it should sputter, cough, misfire etc. I get nothing. (keep in mind that when it was running it ran strong, started easily, idled smoothly).

The air cleaner is removed so there is no air flow obstruction. I even ran a compression check on a few cyl's including #1, they were all in good shape.

Oh and I should add that everything turns in sync so I can reasonably assume that the timing chain and camshaft are intact can't I?

I'd sincerely appreciate any ideas you guys have. I really like this car and it's of course it's paid for. I'm almost to the point of installing a conventional distributor and a carb.

Thanks,


Dave

 

I'm no expert but I'm gonna throw this out and maybe someone can correct me if I'm wrong but have you thought about your coolant temp sensor? I think I read on here once before about that giving someone some start up trouble.

 

Are you reasonably sure you're actually blowing up distributor parts (modules and such) or is that just what you've been replacing and it happens to get the car running again?

 

Maybe fuel fouled plugs from all the cranking??
What did you use to test the spark with? Did you verify spark at the plug end of the wire? If you have spark at the plugs, try cranking and spraying carb cleaner into the throttle body. Possibly not enough fuel from the injectors.

 

Thanks for your responses....

As for the coolant temp sensor I have no idea. Might be worth a try. What effect would this have on my car's ability to start from a cold condition? For what it's worth, the car has been running at a good operating temp (when it ran) and the guage appears to be working properly. Don't know if this rules out the temp sensor, but I'm open for suggestions.

As for the distributor parts, I am not 100% sure of anything except that on the occasions I mentioned earlier the replacement of those parts resulted in my car running again -at least in the short term. Coincidence? could be. That's part of what has me stumped. Some of the modules that I have r&r 'ed have been tested on the bench at the local AutoZone and have showed faults. I replaced them because they were under waranty and to rule them out as causes. Like you, I began to suspect I was going in circles and not finding the root cause. Still don't know.


Yes, I have spark at the end of the wires. I can see with the plug removed from the head but still attatched to the wire. I have suspected a fuel problem but I can both see and smell the fuel from the injectors when I try to start. I have considered some starting fluid as a test here but haven't done it yet. Odd thing is that when it ran it started and ran just fine which leads me to think that there is no major mechanical problem with the fuel system. I am suspecting at this point that there is something in the electronics/computer/spark control/? that is not allowing the car to start.

Also I should tell you that oil pressure comes up to 30+ lbs when cranking so I am assuming that's not the issue - refering to the oil pressure safety switch.

Thanks for the input. I'll let you all know when I figure this one out.

Thanks,


Dave

 

Dave,

I have an LO3 with a 700R4 in my modified 91 305tbi formula. You didn't say, but I am assuming that when your car dosen't start, that it cranks, but doesn't fire, as opposed to not cranking. You have named just about everything that is required to start your car. In my opinion, I think that you do not have an ignition problem. You said that you checked for spark and saw it at the plug. You do not have a timing problem because you set the timing properly by checking for #1 at TDC and you set the distributor with the rotor pointing to #1 plug wire (I might note here, Dave, that if you have a performance or small type rotor, it is sometimes tricky to tell one end of the rotor from the other. I have made this mistake before). You said that when your car is running, that it runs good and also idles good. That indicates that your ignition, plugs and timing are good. You said that you can smell gas and see fuel flowing at the injectors. I would look into the fuel system a little bit further. You didn't mention changing the fuel filter. In addition, there may be a possibilty that there is some water or other contamination in the tank (you would still smell fuel at the injectors, but the engine may not fire). It is quite obvious that you have an intermittent problem, which is the most difficult to solve, but I think that you have already eliminated some of the possible causes already. Fuel problems can cause the situation that you have discribed.
By the way, to check if your temp sensor is causing a problem, just remove the connector from the sensor and try to start your car. If it starts, you can drive it that way for as long as you want to see if that was really your problem.

Good luck,
Don Moore

 

Thanks for the input. I think I had a breakthrough yesterday afternoon....

I've been really busy at work, but I managed to get out at a reasonable time yesterday and stopped by the store and bought a can of starting fluid. Guess what.....It tried to start! Granted it was way out of time and would only run for a few seconds until the starting fluid was burned off...Houston we have a fuel problem.


I'll admit I'm no professional mechanic, but I've done my share of car repairs, and this is my third third gen firebird/TA but the first one with TBI. I had all but ruled fuel out as a cause.

:doh

Here's where I stand....

I can see/smell fuel coming from the injectors. It does seem to be more of a drip than a spray though.

After cranking for awhile trying to get the car to start I can smell a strong fuel smell.

I can tell you that the chances of me having bad fuel is slim since this problem has outlasted a couple of tankfulls and I have been filling my Jeep at the same station and it's running great. (Jeep has a MPI V8).


Any suggestions about diagnosing this fuel problem...Also, where is the fuel filter on this car? I might change it first before going any farther just in case it might be that simple.

Thanks again for your responses!



Dave

 

Dave,

Since your engine tries to run when you spray starting fluid into the tbi, that seems to me that you do have a fuel or maybe an injector problem. Maybe you should start by resetting your timing since you said you turned the distributor after you initially set the timing. If you think that you may be flooding the intake manifold, then push the accelerator all the way to the floor while you crank in order to clear the flooding (the same as you would a carburetor). This may take 15 to 20 seconds; you can do it a few seconds at a time.
The fuel filter on my 91 formula is in the fuel line at the edge of the under carrage just aft of the drivers door. By the way, the spray pattern from the injectors should be cone shaped; if not, then they need cleaning or perhaps replacing.

Good luck,
Don Moore

 

Also, Don't rule out a bad fuel pump or relay.... they can work on and off for a while before they take a total dump...

 

Don- Thanks for the reply...

Since we're talking hypotheticals here, could the lack of proper spray pattern from the injectors be a result of poor fuel volume or low pressure?

If so , I think I will change the filter out first (easiest, cheapest, probably way overdue anyway) and take a look at my fuel flow situation.

I'd say the fact that I have -any- fuel flow from the injectors at this point probably leaves me safe to assume that the pump is running so the relays and electrical for the fuel pump are most likely ok.

Assuming the filter is not the lone problem, the next thing I think I'll do is change out the fuel pump. I'll do a search on the TBI board to see if anyone has any write ups on fuel pump R&R.

I guess if the fuel pump doesn't get it I will change the injectors. None of this is too expensive and all should benefit driveability etc.

Thanks Again,


Dave

 

Dave,

I believe you are on the right track. Just make sure your timing is set correctly, then replace the fuel filter, then check your injectors. Leave the in tank fuel pump until last. That will really be a bear. The rear end and possibly some of the exhaust system will have to be removed to get the tank out for access to the pump. At least that is the case with my 91 305tbi. By the way, when you turn the ignition switch to on ( don't crank the engine) you should be able to hear the fuel pump relay energize and alow fuel to flow for 2 seconds and then de-energize. When you crank the engine, fuel will flow continuously.

Later,
Don Moore

 

My 88 lo-3 had a problem like that and I tried everything Ign. to fix it! Finally my wife got tired of me bitchin" about it and bought me a fuel pressure tester at AZ. And I found it was only putting out 7 1/2 lbs of pressure. I put in a new pump and 13 1/2 lbs cured the problem. I had most of my starting problems after it was warmed up. As the problem got worse, even cold starts got to be a pain. If I had bought the pressure tester before all the ign. parts. I could have saved the price of the tester!

 

Looks like I'll be doing a fuel pump and filter this weekend...maybe sooner if I have time.

One question for you guys that have in-tank fuel pumps...

I haven't had mine out yet so I don't know what the pick-up looks like but is there any way to adjust the pick up so that my car doesn't suck air during hard cornering. I will be using this car for some weekend AutoX once I get everything sorted and I suffered from extreem fuel starvation turning corners with anything less than half a tank (maybe 2/3). Obviously I don't have a 1LE tank to swap in. Just wondering if there's anything I can do while I'm doing the pump?

 

When you change the pump, get a new strainer with it. I got my pump at Napa for I think 49.00. It was a wagner pump and is doing fine. I auto-x too and the best advice I can give you is fill up the tank before you hit the track! My rear end was always loose with less than a full tank. I think the weight of the fuel helped my traction a bunch. My form. is light in the rear anyway and you know, they race in the rain too! I would still check the fuel pressure first before buying the pump. I'll warn you first, the tester and the pump are about the same price.

 

Thats unusual to have fuel starvation around corners. Ive never had a problem with that unless the tank is almost completly empty. And I mean empty. I think all of the fbody EFI cars have the baffling (either that or I have a baffled tank). Are you sure your fuel level sender is accurate? Thats another part thats worthwhile replacing if your there.

On a side note, if the car doesnt start while cranking the engine will flood, the plugs will foul, and itll do nothing even if its being given spark. If you want to remedy this, crank the engine with the fuel injectors disconnected to clear out all the fuel before trying a restart.

 

No it's not. It depends on the year but they made SEVERAL different tanks in these cars over the years, with different capacities, and different methods of baffling.

My Mom's '86 TPI would start having issues just under a half tank! (during extremely hard cornering)

My 83 CFI will run down to about a 1/4 tank before starving in HARD corners.

I have read that the 1LE cars have the best baffling in the tanks, but have not visually verified this. I don't have any recomondation other than to fab your own baffle. Being aware of vapors in the tank of course.

 

hmm... I had a similar discussion with a mechanic friend awhile ago and the conclusion we came to was that the later f-bodies actually had ok baffling. I havnt varified that by visual inspection, hence the 'think' but ive never had much trouble with my '88 under even wild cornering. I guess the best way to find out would be to ask owners of similar year/make/model cars as to whether its a problem or not or jsut get another tank/add baffling to the present one like tom said.

 

24x7, I think it depends on what you define as hard cornering. Your car and mine probably have the same tank and you're right while street drivig, even somewhat aggressive street driving, I don't have starvation issues until I'm in that 1/4 tank or below range.

But.....at the last AutoX I attended (I'm not a regular at this point) I started with about 1/2 to 5/8 tank. Made 4 runs about 1 min each. Fuel level dropped some but not a huge amount. It was enough to cause starvation though. Now keep in mind that in AutoX, unlike most street situations you are hard right then hard left then hard on the brakes into a corner etc. That moves the fuel more than a tight on-ramp due to the changes in direction. Also the car achieves some killer G loads on the big 50 series Kumhos. I love the way the Formula handles. Much better than the two TA's I had previously. I attribute part of this to the fact that this is the only non t-top f-body I have owned.

I suppose there is a possibility that my strainer is nasty or clogged up and this may also be a factor in my ability to pick up fuel in the corners. I'll know soon when I pull the pump probably on Saturday.

Have a great day,


Dave

 

the pump can be a bitch to get at, unbolt the rear and remove it or let it dangle by the lcas and push it out of the way.. then drop the tank out.. kinda a pita but more time consuming then hard..

 

my 89 iroc would starb for fuel when cornering if it had less than 1/4,but my 92 rs doesn`t have any problems till it pretty much runs out of fuel i have change fuel pumps in both of them the 92 has baflings in the tank that the 89 iroc doesn`t plus the strainers on the newer cars are better