bangbgC6

The title of this thread is a comment posted by 65Z01 to Cajun86 concerning Engine "Problem"

I did not want to jack Cajuns thread but I have a question concerning my '89 L-98/auto with 176,000 miles.

2 Months ago due to a clogged radiator it I blew a head gasket, the no 8 hole specifically.

Got the heads done, installed 1.6 rockers, new wires, hoses, rotted out the rad. etc. and put it back together It runs fantastic, until yesterday morning.

I was crusing at 45, the limit went to 55 and as I pressed the accelerator it just laid down and died. I pulled into a local park and attempted to troubleshoot.

It will start but idles irratically, if you press the accelerator it dies, you can repeat this same process over and over with the same result.

Came home and searched the archives for some clue, I believe it is not getting gas so I have focused on the fuel delivery.

I pulled the fuel filter and it was clear, seemingly fine.

This is where the confusion starts for me, this is my understanding from the threads I reviewed.

The FPR triggers the FP for 2 seconds when the ignition is switched on, until the OPS sends a signal to the ECM of 4lbs of oil pressure. I confirmed that indeed the FP runs for 2 seconds and does pump approximately 4 oz. of fuel each time the ignition is switched on.

The OPS seems to be fine in the car, giving both OP & OT readings through the dash displays. Is it possible for the OPS to give information without triggering the FP.

I am probably not explaining this well but what I figured I would do today is get a new OPS and FP relay. If that does not help I would get a new FP and drop it in.

What am I missing? There is no pressure at the Schrader valve when the motors not running. I am going to get a gauge to put on the Schrader valve for FP anyway so that will be soon.

The motor runs and sounded great before this so I am thinking it is just a coinsidence that it happened and does not have anything to do with the recent mechanical work.

The statement from 65Z01 just kind of confuses me, if the FPR is not working how does that affect the car?

Thanks in advance for Advice/opinions.

Redeasysport

I think you are confused. There is an oil pressure sending unit and an oil pressure switch 2 seperate things. The switch keeps the fuel pump running the sending unit supplies the readings. It does sound like the FP is a problem if the filter is fine.You need to get the gauge on it and watch what happens when it is running.

Usually when the FPR fails it is because the diaphram ruptures and allows gas to be sucked in via the vacuum line. It will make it hard to start when warm restart happens due to flooding. It will not starve the engine when it fails. That is if you mean the Fuel Pressure Regulator ( the usual meaning of FPR) if you mean the relay itself then it will make it hard to start until the OP switch kicks in after pumping up the pressure enough with the starter.

ZumZum

I'm going to be following this thread. Bang's symptoms is exactly what I've been experiencing on an intermittent basis.

It usually only happens after hard acceleration. I've had a pressure gage hooked up and the pressure is fine

bangbgC6

Oh, I'm definitely confused.

#1. When The shop did the heads the guy made a comment of," you might want to check the fuel pressure regulator, because it looks like the motor was running rich." When I looked I could find no way to adjust it so I put it back together as it was.

#2. It definitely cranks a long time to start when warm, cold is instantaneous. (I think I mis-interpreted the FPR in the threads I read as Fuel pressure relay instead of Fuel pressure regulator).

#3. Judging by the fact that when I turn the key on the Fuel pump does indeed run for the specified 2 seconds, the relay may not be the problem.

Thank you for the insight.

I feel it is something minor I just need to pinpoint it. I will keep the thread updated for others as I go.

BTW- where is the Oil pressure Switch, I know where the sensor is.

Redeasysport

Pull the vacuum line off the FPR and smell it if it is wet or reeks of gas it is bad. It will make the car run rich when warm restarted.I can't tell you the location since I am a LT1 guy.

bangbgC6

It is easily accessible, located immediately under the plenum on the intake.

I will check that first before buying the other items I mentioned.

R & R couldn't take more than an hour if needed.

More to come I'm sure.

Thank you for the tip.

AGENT 86

If you hear the pump running for 2 seconds, the relay is good. You say you have no fuel at schrader valve. If both of those are still true, pull the pump and see if pump sock is clogged and if there is a leak between pump and top of tank.
Pressure gauge is a must for the tool box.
If you apply 12 volts+ to terminal "G" on the ALDL connector, you can run the pump as long as you want. This can help when diagnosing fuel delivery problems.
Here is some info from my 86 manual.
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
I believe there is a difference at the 89's relay, so here is a pic of the 89's fuel electrical.
http://members.shaw.ca/agent86/89fuel%20copy.jpg

rick lambert

You're on the right track by getting a fuel pressure guage! Hope you also have a Factory service manual for your specific year? Sounds like the fuel pump relay is fine!

bangbgC6

Thanks for the valuable info, this forum is such a value in that regard.

Last night when I got home I pulled the vaccum lime off the fuel pressure regulator, I will avoid using acronyms so I am not confused, on the advice of 65Z01. It did indeed have the strong smell of fuel.

Thinking back, one thing that I failed to mention is that on Sunday am prior to my leaving home something happened that was as immediate indicator of something amiss, that I of course dismissed without a thought.

I had opened the hood to visibly check everything, since we had just gotten the motor up & running. When I started it there was a really loud racket from the area of the injectors that subsided the longer the motor ran. I have run/started the car often with the hood up and have never heard this before.

After about 45-60 seconds the noise was gone from what I could tell.

The car ran great all the way up/down the Cajon pass until it laid down 38 miles later.

I am now thinking that it was the injectors running dry until whatever it is that failed pumped up enough pressure to charge them(probably at a seriously reduced volume). Then whatever it was(fuel pump/fuel regulator) finally gave up the ghost.

I am leaning towards fuel pressure regulator and will probably replace it as soon as time permits.

Agent 86, as far as doing that inspection, I believe I remember that there is an access panel that allows easy access to that area for this very type purpose. Isn't that panel is under the carpet/insulation in the area behind the seats?

Also some asked recently if the FSM(sorry I slipped) field service manual is available on CD for use on a computer. Does anyone know if it is.

Pressure gauge for the Schrader valve will be bought immediately.

more to come.

Thanks for your time and efforts.

Redeasysport

Change the FPR it will start better when warm.Your erradict idle may go away to as you were pumping gas into the intake via the vacuum line.You need the FSM book it is available at Helms web site or sometimes a deal on ebay. It was never put on CD.

I had a similar noise when I did my intake it went away and never came back.

bangbgC6

Installed new fuel pressure regulator. Still is not right.

Got the fuel pressure gauge and tested fuel pressure. It is 42psi cranking and 40 psi when running. Stays at 40 for about 1 hour after shutdown, decreases to about 25 psi after 2 hours shutdown.

The car fires up instantly, but only runs for about 1-2 minutes when idling before it quits. If you try to increase throttle it stumbles and chokes until it stalls out. You can repeat this same pattern indefinitely, always fires instantly and stumbles.

I don't think it is the fuel pump; I do not think it could be the fuel pump relay since when the ignition is switched to on, not to start, the fuel pump runs for the prescribed 2 seconds to energize the system.

I am now not sure that it is fuel related at all.

WickedVetteLT4

Hmm... Same symtoms of my car for the most part. Restarting when hot is a pain and take longer than it should.

I know for a fact my car is running rich. When the car is idling, all i smell is fuel and if you stand behind the car, the exhaust reaks of it!

I made a post asking about the issues my car is having but it seems to be somehow related to this judging off the symtoms...

Redeasysport

And it may not be. Did you pull any codes.? If it is maintaining Fuel pressure during running it probably is not.Clean out the TB IAC passage. It could be starving for air. Your O2's could be toast. You ignition module could be toast. Your injectors could be stuck open.Try pulling codes at this point and follow the FSM flow charts.

CFI-EFI

What happens to the fuel pressure as it dies? If the pump, sock or filter can't pass enough fuel, the pressure will drop before and as the engine dies. Otherwise it should drop after it dies.

The problem absolutely is NOT the fuel pump relay. When the ignition is first switched on, the computer, not the fuel pressure regulator or the fuel pump relay, activates the fuel pump relay for 2 seconds. The activated fuel pump relay powers the fuel pump. When the engine is cranked, the distributor sends pulses to the computer. These pulses tell the computer that the engine is turning, and the computer once again activates the fuel pump relay. The computer continues to power the fuel pump via the fuel pump relay as long as the engine continues to turn, whether it cranking or running. Then, once the oil pressure reaches ~4 psi, the oil pressure switch closes and sends 12 volts around the fuel pump relay, directly to the fuel pump on a circuit parallel to the fuel pump relay circuit. The oil pressure switch does NOT send power to the fuel pump relay. The oil pressure switch is a back up in case of fuel pump relay failure. You would never know if the oil pressure switch failed unless the fuel pump relay failed, also. And as can be seen from the above, the oil pressure switch does NOT act as a low or no oil pressure engine shut down. If the oil pressure dropped to zero and the oil pressure switch opened, the fuel pump relay would continue to power the fuel pump.

RACE ON!!!

bangbgC6

The pressure remains constant as it dies. The presure does not drop however, after it dies, staying at 40 psi, it does eventually drop after about 1 hour or so to about 25psi.

Pulling the codes is probably the best thing to do at this point.

I keep going back to the upper end work that we did. I have a real sneaking suspicion that it is somehow related. It ran strong for about 100-125 miles after we got it back together before this problem showed itself.

Thanks again for the input.

I'll be reporting in.

CFI-EFI

Your description of it dying sounded a lot like it was starving for fuel. This reports proves that not to be the case. That description and the title to the thread was the reason for my last post.



It's never too late.



???

RACE ON!!!

bangbgC6

The car blew the passenger side head gasket. My son Adam and I pulled it apart and got the heads done, and just got it running again when this happened.

Not being professional mechanics its very likely we inadvertantly caused the problem.

I do feel it is something really simple, I just have approached it the least expedicious way. If it was my only car I'm sure it could get fixed much sooner. I just don't have time during the week to even look at the car. Actually, looking at it is all I can do at this point and I can live with that.

When I filled it up on the last day I drove it and it cost me $70.00.

By this weekend when I am driving it, it would have cost me almost $85.

Who says a Corvette is not economical, sometimes it's like money in the bank.

CFI-EFI

More often than not, new problems are the result of recent work done, even by (although less often) professionals. I see no connection between the work you did and a reason to have fuel delivery problems. Your symptoms do suggest a fuel problem, but your fuel pressure readings rule that out. Have you checked for codes as previously suggested?

RACE ON!!!

anesthes

My truck started doing this last week. Drove me nuts. Checked everything, did a tune up etc. Same symptoms.

Unplugged the ESC module. Runs fine!

Obviously either a bad module, or bad knock sensor. Probaby retarding timing or something too fast and stalling it.. Might not be your problem.
But unplug your ESC module, and fire it up. See if it runs better.

Have not touched the truck since. I'll get around to changing the knock sensor and or module this weekend.

Another thing, if that head gasket wiped out the 02 sensor (with coolant), it could be having a fit if it makes it into closed loop.
The 02 logic in the '89 bins ($6E) is rather lame. As long as its crossing quick enough, it will enter closed loop but it could be way
wrong.

-- Joe

firstvette 2

A couple of things no one mentioned was perhaps your air filter plugged up for some reason making the engine would starve out. As you had the heads off there could be a problem with the TPS (throttle position sensor) connectors or the sensor itself. The TPS lets the ECM know what the driver demand is. To quote the service manual "By monitoring the output voltage from the TPS the ECM can determine fuel delivery based on throttle valve angle (driver demand)." The TPS is a simple potentiometer whose output varies between .5 volts at idle and 5 volts at full throttle. I'll bet it just loosened up. If you get a code 21 or 22 then there is a problem with the sensor itself.
Lets fix it so you can come visit me!!!