AnnieG

So my husband has an 84 Corvette, it doesn't get used heavily, just for casual use. Was running great, then about 4 months ago he was driving and got on the gas and suddenly the car began running rough, stalling, not wanting to start. He made it home and has been trying to troubleshoot repair ever since.

The car will start but won't stay running. Rough idle, backfires, stalls, etc.
He's done a ton of work already but still has the same result:

-rebuilt TBI units
-replaced fuel pump relay and harness
-replaced map sensor harness
-replaced map sensor module (made no difference)
-temperature sensor to guages replaced
-fan switch temperature sensor replaced
-electronic spark control module replaced (made no difference)
-checked for fuel spray (no fuel spray at start) but fuel pump is coming on
-checked timing, found loose rotor (tightened)
-disconnected vacuum hose from map sensor and start - car idles high but evenly, and stays on without having to press on accelerator. Can see fuel spray from injectors. Only stays on about 5 seconds, then ceases idle and dies.
-checked catalytic converter & exhaust
-timing seems to be right
-computer seems to run the car well for 5 seconds, then everything goes bad and it dies.
-not throwing any codes, unless he disconnects a sensor

Any suggestions out there? He's really been pulling his hair out over this and isn't sure what to do from here.

gwbutch

Is the oil pressure coming up during the 5 sceonds it is running? I'm not sure if the motor is dieing because the gas is stopping or if the gas shuts off because the engine has stopped. The fuel pump relay is tied into the oil pressure switch. The oil pressure switch is bypassed while starting, but then after a few seconds, if the oil pressure does not come up, then the fuel pump is shut off.

oldalaskaman

change the fuel filter

AnnieG

@gwbutch, thanks for the response - Yes, he has checked the oil pressure switch and it is functioning properly opening/closing as it should. He's tried so many things, difficult to remember everything when typing the post. We are open to any suggestions.

AnnieG

@oldalaskaman, the fuel filter was replaced within the past year. Considering he only puts about 1K miles a year on the car, do you really think the fuel filter could be the problem?

69427

Has he checked the fuel pressure?

I had a similar issue this spring with my '84. Checked everything under the hood, and everything was fine, could hear the fuel pump run (confirming the ECM and relays were working), but the engine wouldn't keep running. I put a pressure gauge on a tee in the fuel line and discovered that I only had about a pound and a half of fuel pressure. I pulled out the fuel pump (amazingly easy!) and examined the pump. The rubber fuel line at the pump outlet had softened and ruptured (I believe due to alcohol in the fuel), bleeding off most of the pump output. I replaced the short hose and put the pump back in. That fixed the problem.

Not saying that your vehicle issue is the same, but I do recommend verifying that the fuel pressure is at the level it needs to be at to allow the engine to run correctly.

Good luck, and keep us posted.

AnnieG

@69427 - Where is the T in the fuel line you are talking about to check pressure. He has a hard line between the TBI units, but no place he can see to connect a gauge for checking pressure. Sounds like you had a very similar issue. He's read other info about connecting a gauge to check the pressure but hasn't figured out where to connect it. Please let us know what you can about the location to do this.

Tom400CFI

Create a "T" between the filter and the rubber hose near the right front of the engine, down by the frame. "Backfiring" is a sign of lack of fuel. That, combined with "lack of fuel" being a common issue on CFI engines...I'd be ALL OVER checking fuel pressure. Didn't see "Fuel filter" on the list above...

You might want to brush up on that circuit. The oil pressure switch is not capable of shutting off the fuel pump.

hemivett

Mine had 14lbs at the rail, but still spit and sputtered while driving, so I did the Walbro 255 pump, and now she runs great. It could be your pump has just enough to fill the lines and filter, and when you start it, it basically runs out of gas.

Fuel pumps on Vettes are easy to do. Tell your husband to leave on the old filter till its been ran for a couple minutes. This will catch any crap that may be in the lines, when it gets a shot of real fuel pressure.

Like Tom says, get a fuel pressure gauge on there. Id be willing to bet you're very low, if not 0, after you start. h

AnnieG

So glad I posted here. He'd gotten to the point that he thought it was the computer that went bad. I suppose it still could be, but he has not yet checked the fuel pressure. Had him read the responses and his next step is to check fuel pressure and possibly new pump & filter. We will post results. Thanks to all of you for the quick feedback!

mtnmanut

mtnmanut

i posted a lurk,because i'm getting up there and my memory sucks.anyway i recalled what got my attention. several years ago i had a very similar situation with a chevy pick-up.i believe it was an 86 or 87? after exhausting what i thought was every option in trouble shooting,i finally stumbled upon the problem. it turned out to be the icm. ignition control module. i don't believe it was the module itself as much as the di-electric grease that insulates it. the old 20 yr old grease had dried up. i re-greased,reinstalled and at that point ran fine. since it was 20 some yrs old.i replaced it with a new one as an after thought not wanting to have the same problem again. not saying thats your problem,but. good luck sometimes the simpleist is the easiest to overlook.

84VetteMan205hp

mmm this is interesting

AnnieG

First, I would like to thank everyone that posted suggestions, and so quickly...you all are terrific!

So, today the husband took the time to pull the fuel pump. The internal hose is ruptured and the strainer is in terrible shape. There is no doubt that this is a major problem, if not "the" problem. He is working on installing the new fuel pump and the various parts that go with it. If all goes well, his baby will take him for a ride tomorrow, and I will get my garage back.

Thanks again!!
Annie

hemivett

Congrats May the rest of your days be sideways! h

AnnieG

Sheesh, the husband decided to order the Walbro Pump and 1984-1985 Kit from Racetronix instead of buying from a local auto parts supply. So now he has it all...and isn't sure what to do with some of what's included. No instruction sheet was included, but there is an extra clamp with some type of connector spade, a tiny plastic part, and a large safety pin included with the kit. I've emailed Racetronix but thought I might get faster response from someone here.

Has anyone out there bought the Racetronix kit and know what these parts are for?

AnnieG

"Real men don't ask for directions; they make their wife do it."

LastC3AZ

not a fan of the after market pumps for these cars ..... simply drop an 85 pump in and call it a day .... it will give you more then enough pressure ..... and a lot less hassle ... IMO ......

69427

Is it possible for you to post a picture of the kit parts, and perhaps the collective here can figure out where all the parts go?

jhammons01

First off, the info about the oil pump was debunked by Tom, Thanks Tom (and why won't that misinformation ever die for good?)

Second, the 85 pump is not the solution and has lead to many debates on the forum.

Thirdly, the issue with the aftermarket pump is that it probably fits on many different years, that spade connector may be a sensor that does on exist in the '84. So, Hubby is looking for a female pigtail to hook on that spade connector and there may not be one in that wiring harness.

As an example, if you have an early '84 and you buy an OEM replacement radiator, there is a low coolant level port in the radiator and you have to buy the sensor to plug that hole....now you have a spade connector staring you in the face with no wire on the '84 to connect to it.....every motor head that looks at your car ask you why you didn't hook it up......Your after market pump may have something on it for other years.....

hemivett

@ LastC3...Everybody replaces with a Walbro. (I did) Seems to be the factory replacement, or at least the go to aftermarket. (Better quality than factory IMO)

@Annie.... Some of the parts are extra, and/or for other models. For the most part, he needs to focus on replacing the pump, and if he needs any of the extra parts to get it together, then use them.

I want to caution you/him. A lot of people like to hook up the old pump, and the next thing you know it spits gas, you freak, sparks fly, and your on fire! So dont be tempted. Test the new one after its installed.

The pumps on these cars, are the easiest to replace Ive ever done, (Ive done many) The main thing is to clean everything real good before pulling the old one. Use a small wire brush, and a vacuum, before removing. h