red86man

As the thread title suggests, my '86 Coupe has been in a no start / no run condition for over 6 months now. We've got a few days of warm weather for the next couple days here in Upstate NY, and I'm hoping to finally get her running and tear up some street before the snow and cold hits again. I'm hoping for a miracle and would certainly appreciate any and all helpful suggestions from the forum.

Let me start off with the major things that I've done or replaced, which are as follows:
- Completely rebuilt distributor - every part, except for the main casting is brand new including the coil.
- New spark plugs and wires.
- All the above were done 2 weeks before I started having issues with the car and are in working order.
- Timing set properly mechanically and electrically, all cylinders compression-tested SAT.
- Noid light tested injectors - all of them blinked properly, tested SAT.
- Replaced TPS and set to 0.54V with DMM.
- New PCV, Fuel Filter, Fuel Pump and Filter Sock and FP Relay.
- Totally cleaned up Fuel Sending Unit prior to installation of new FP.

Let me reference two other threads I've posted to recently talking a little about this issue:
- http://forums.corvetteforum.com/show...94&forum_id=48
- http://forums.corvetteforum.com/show...post1553491057

Here are the symptoms:
- Car doesn't start, or, on the few occassions when it does start, it dies within about 20 - 30 secs.
- Key on - Fuel pump does not energize, no fuel pressure.
- Key start for 3 secs. - Fuel pressure rises rapidly to 42 psi on gauge.
- Upon release of the key to On position, I hear fuel pump noise for 2 secs. and also hear an internal suction / gurgling noise coming from the area around the Fuel Regulator.
- Both Fuel Pump noise and FR noise happen simultaneously.
- After the 2 secs. of noise from FP and FR, the pressure immediately drops 2 psi to 40 psi.
- Afterwords, with key on or key off, the pressure drops from 40 to 30 psi in less than 1 minute. Completely depressurized in about 3 minutes.
- No start, No run.

Any thoughts or suggestions would be most welcome.

rick lambert

Well, obviously you have a fuel problem-you replaced FP, FP relay, and fuel filter-BUT, there's a couple things that seem odd-at least to me. When you turn the key to the on position-that is when you should hear the FP relay priming the system-NOT after you turn the key from the on position-did I read that right? another thing, is your fuel pressure is dropping to fast if it goes from 40 to 0 in 3 minutes-which to me would indicate you have an injector(s) problem or a FPR problem.I haven't experienced the gurling sound-but try to isolate it. You may even want to check your fuel lines. Have you tried starting fluid or spraying gas into the intake to see if it will start and run? Obviously you have spark if it starts on occassion.And I would think the injector fuse must be OK-neverthe less I would also check that.Lets see if we can't help you get this puppy running!

REDC4CORVETTE

Do you have an OEM regulator on the car and when you replaced the fuel pump did you reinstall the pulsator back in line?

JAKE

The first thing I's do is wipe the slate clean. I would not consider what I'd already done to be correct and working properly. Forget all that, because the engine still won't start and run so there still must be something that hasn't been done correctly. I'd go back to square one and start all over.

Changing parts isn't the way to go about it. Diagnose then, if necessary replace parts.

I'd begin by diagnosing and fixing the obvious problems/malfunctions: the fuel.

I'd identify and fix is the fuel priming problem. There's something going on there.

If you don't hear the pump energize (turn on) and prime the rails as soon as you turn the ignition key to "On" (not Start), I would first suspect the relay or the wiring to and from the relay. You should hear it for about 2 seconds. This should happen BEFORE the engine even cranks.

Next is the fuel pressure dropping so quickly. You have a leak some where. It can be in the engine compartment, one or both of the fuel lines leading to and from the tank, filter AND/OR at the pump itself.

Keep us posted.

Jake

bluealtered

Ok, now my turn to show what i don't know, what is noid light testing of the injectors? joe

red86man

Rick, good to hear from you again. Yes, that is correct - the fuel pump energizes audibly after key-start to key-on, although the fuel system pressurizes visibly on the gauge immediately to 42 psi after key-on to key-start. Scratching my head on that one, too. It just doesn't make sense.

When I first started having the issues with my car 6 months ago, the fuel pump always energized as it should - key on, fuel pump noise for 2 secs. This scenario is something I haven't noted before.

I recently isolated the location of the gurgling / suction noise, which appears to be coming from the area under the center of the intake manifold where the EGR valve (I believe) mounts to the manifold. Is it possible that a bad EGR valve could be the cause of these issues?

rick lambert

You're also indicating the gurling sound is comming from the area of your FPR-hmmmmmm! Like I said, get some gas in a spray bottle-or some starting fluid-you'll need help-someone to apply pressure to the peddle and crank while you spray-A LITTLE goes along way. If it starts-you definetly know it's a fuel delivery problem-which I suspect!
and hearing where the gurling nosie is comming from further leads me to belive it MAY be a FPR. You are doing the right things and I'm here to hopefully help. Good luck and keep us informed.

ittlfly

Have you pinched off the lines to and from the gas tank in proper order to determine which part(s) are failing? It's easy and since this appears to be a fuel problem, it SHOULD point you in the correct direction.

JAKE

I suspect the FPR too.

Jake

Jerris

You seem to have good enough fuel preassurs before starting to start the car. Does fuel preassure drop while cranking or on the occasions when it starts? If so your problem may be plugged catelytic converters as this back preassure would kill all vacium in the intake that gives the signal to the fuel regulator and in fact may be shutting off the FR and causing the gurgling sound as well as allowing the pump to shut down.
Try pulling the vacium line from the FR and see if the engine wants to start and idle for a short time.
Low vacium in the manifold can also fool the ECM into thinking that the engine is not running and cause it to shut off the injectors. Had this happen to me once with a customers 450 Benz due to blocked Cats after he ran a tank of leaded gas in the tank and it t ook two weeks to find the problem. When I disconnected the exhaust to pull the engine to check the timing chain, used the key to bump the engine to get at the torque converter bolts to my surprise the engine started and ran fine. Removed cats, no more problems ( this was 16 yrs ago when cats were new and leaded gas was still available at the pumps)
If it does try hooking up a vacium guage to the manifold and see what the cranking vac looks like. If it is low I would suspect the cats.
If this is not the problem then I would suspect a problem with the EGR sticking open.
Hpoe this helps
Jerris

-js-

Here is some info I haven't seen anyone give you that should help you out.
Most consider the Helminc factory manuals a must have. They are costly compared to the bookstore Chilton types and once you have one you will know why.

A link to the l98 start sequence http://corvettebuyers.com/c4vettes/l98.htm
A link to the factory service manual supplier http://www.helminc.com

CFI-EFI

Not likely. The fuel pressure differential between max vacuum and zero vacuum is about 10 psi of fuel pressure. And that is with the fuel pressure rising as the vacuum drops. Zero manifold vacuum would cause the regulator to max out the fuel pressure.

RACE ON!!!

rick lambert

I have to agree with CFI, besides, I personally have had a few clogged cats-and the motor still would start-not to say it couldn't happen since you seem to have experienced this.

Redeasysport

If I read this right your fuel pump relay does not engage when you turn the key to on?If you crank it it will come on?Bad relay,oil pressure will also turn the pump on.Check fuses.


The FPR looks like it is the likely candidate for your leakdown although there is a check valve in the fuel pump line that should be checked first by using the above mentioned hose pinching

Neither of these will cause the car to die after starting.Put your pressure gauge on when you start it to see what idles at.

I would solve the fuel delevery problem then go from there but I suspect there is more to the problem.

Jerris

Thanks CFI for the correction, you are absolutely correct on the way the FR works, sorry for the confusion.
Rick I still wouldnt discount the cats yet though as if the back preassure builds in the manifold the gurgling sound could be air leaking past the EGR although not the rapid release of preassure after cranking.
It is easy enough and does not cost anything to check for blockages in the exhaust with a vacium guage or at the tailpipes.
Apologies again for the *** backwards advice on the FR.
Good luck
Jerris

CFI-EFI

The problem with checking back pressure, is that you have to get it running first. Drop the pipes at the exhaust manifolds.

RACE ON!!!

rick lambert

Oh, I wasn't saying the cats couldn't be the problem, I was just saying I haven't experienced that situation, where as the cats have caused ME that type of problem-a no start-no run situation, my experience has been strickly a poor performance problem-like running out of gas or air flow problem.

madmike

ill throw my two cents in , I would start with fuel air spark, check the plugs. Are they drenched in fuel? that gurgling could be injectors flooding the engine. I think your spark is ok cuz you said it fired and ran for a few seconds. Does this do this often? If it runs for a bit consistent its probably not your distributor and its healthy. is this after its been sitting for a while? engine driy with just the right amount of gas before flooding? check for flooding first. If plugs are bone dry then squirt some starting fluid down the plenum and it should start. And slowly eliminati the fuel rail injectors, fuel pressure regulator and fuel pump. If plugs are wet and never starts again, check your spark. Air is usually not an issue unless a potato got stuck in your throttle body or you dropped a timing chain and neither air nor water is getting into the combustion chamber. Air Fuel Spark... Hope you get it running soon, next best thing to flying ..Corvette

red86man

Wow, many informative responses - thank you all! After reviewing your responses and researching the flow charts and wiring diagrams on http://members.shaw.ca/corvette86/, I ran a few tests. Here's the update:

Symptoms already noted:
- No start / no run. Wants to kick over, coughs and sputters a bit, but no run.
- Fuel pump continues to run audibly for 2 secs. AFTER cranking and not after initial key-on.
- Gurgling / suction noise occurs simultaneously for 2 secs. with audible fuel pump noise and seems to be coming from the EGR valve mounted underneath the intake.
- Fuel system pressure dumps much too quickly (40 psi to 0 in less than 3 minutes).

New Tests and Observations:
- Pulled the vac line on the FP and tried cranking several times - no start, fuel system continues to dump quickly.
- Clamped fuel pressure line after cranking and fuel system pressurization, pressure continues to drop quickly.
- Clamped fuel return line after cranking and fuel system pressurization, pressure continues to drop quickly.

Conclusions:
- Still not entirely sure why the new FP Relay is not energizing the fuel pump at key-on. The wire insulation has pulled back on 3 of the incoming wires to the FP Relay connector, which may be part of the problem.
- My best guess as to why the fuel system pressurizes after key-start might be a result of the oil pump relay taking over for the FPR circuit and energizing the FP after cranking and oil pressure rises over 4 psi. Seems like this might make the most sense, given the electrical set-up.
- The fuel pressure dumps quickly when either the fuel pressure or fuel return lines are clamped. This is a most curious situation. The fuel is obviously dumping somewhere due to a fuel system component malfunction, and most likely it's not going back to the tank. My best guess is that I may have an open fuel injector that's dumping fuel and causing the rapid pressure drop.

Again, your thoughts would be appreciated.

ittlfly

Correct me if I'm wrong here...... but if you are still loosing FP with both lines pinched off, then the fuel must be bleeding off through the injectors as the FPR vacuum line is dry. As mentioned before, I'd pull the plugs to see if they are drenched. Check your dipstick for excessive gas smell in the oil. If all that gas is entering the cyls it will wash the rings and contaminate the oil.