I'm having a problem starting my car. It died on the side of the road and wouldn't restart. I had it towed back to the house and looked the problem up in my service manual where everything pointed to the distributor. I have replaced the rotor, cap, module and coil. The car still won't turn over. I had the battery tested and it's still good. I'm about to test the fuel pump. If that turns out to be the problem, how difficult is it to replace it yourself or should I take it somewhere? But if it still don't run, what else could it be? I don't want to pay for a part I don't need.

 

You give a very poor description of your problem! Does the starter motor crank the engine or not? Also, you should ALWAYS state what year vette you are asking help for. They are not exactly the same year after year.

 

Sorry. It was my first post. I have an '84 and it don't seem to be the starter because it tries to turn over up until the battery dies. It's like the engine isn't getting any fuel. The fuel pressure must not be high enough. I took the in-line fuel filter off and gas leaked out so nothing's clogged up. There is voltage going to the fuel injectors but nothing's coming out into the engine itself.

 

All IC engines require spark and spark at the right time, they need fuel and air and in the correct ratio, and they need cylinder compression. So......use a timing light during cranking to determine if you have spark and spark at the right time. Use a fuel pressure gauge see if you have the correct fuel pressure (35-42 psi) and see if it holds up for a long time with the ign off. Rapid pressure drop indicates possible leaky injector or a defective check valve in the fuel pressure regulator. Use a noid light (available at parts stores), or make one with an LED and a series 680 ohm resistor and connect to the unplugged injector socket during cranking to see if the injector is being pulsed. Homemade light must have the LED anode connected to the injector wire with 12v on it. You can try it both connections if you want to. You can also spray starting fluid into the intake during cranking to see if the engine will run momentarily, proving you have a fuel delivery problem. If everything checks out ok and it still won't start, then measure cylinder compression on each cylinder.

 

What about the fuel relay switch? Could that possibly have something to do with it? If it went out, won't it prevent the fuel pump from working?

 

What about the fuel pump relay? Isn't there a test for that?

 

Let me get my chastising out of the way first.....STOP GUESSING AND START TROUBLESHOOTING. Throwing parts and $$ at the car hoping to solve the problem is fine....if you're independently wealthy and have no time constraints. But since you're driving an 84, I'm guessing that isn't the case. Soo.....do what the rest of us schlubs do, and troubleshoot the problem in a methodical manner and you will find and repair the problem.

They need 3 things....and 3 things only to run:

1. Suitable compression.
2. The correct mixture of fuel and air.
3. A suitably strong spark delivered at the correct time.

That's it. If those 3 conditions are met, they run. If one or more is missing or deficient, they don't run correctly or at all. See...isn't this easy?

Now...let's start with the simple stuff. Let's check and see if you have fuel pressure first, and HOW MUCH you have. On an 84, there is no schrader valve to attach a gauge to. You will need a T fitting and clamps...attach the T fitting just in front of the fuel filter, and run the hose to a low pressure gauge (0-15). Run 12V to the fuel pump terminal (G) on the ALDL to energize the pump full time. Tell me how many pounds of fuel pressure you have.

Checking fuel pressure on an 84 is a PITA. What I did on my 84 to check pressure is remove the crossover tube and have a port put on it (any hose and tube shop can make it for you), and a fitting on my low pressure gauge....it looks like this.



It beats the hell out of climbing under the car and using T fittings and clamps.

Anyhow....tell me how many pounds of fuel pressure you have and we will go from there.

 

You do the fundemental things first and then you branch further out from what you discover. Do you have spark? Is the spark at the right time? Do you have fuel pressure? Will the engine start and run momentarily on starter fluid?
You want to worry about relays and other stuff and you haven't yet found out if you have fuel pressure. If you found out first if you have fuel pressure, then you don't have to even consider fuel pump, fuel pump relay or anything else. Spark is the easiest thing to test so do that first, then measure fuel pressure. Cylinder compression is last. Post what you find and we will offer more help.

 

I'm sorry to hear that...

Let us know if you need help. We do regular service for many C4 owners.

-Adam

 

I'm fairly certain the 84 also has an oil pressure switch, like newer models whereas if the fuel pump relay fails the oil pressure switch will cause fuel delivery after cranking the engine and oil pressure reaches 4 pounds....maybe someone with an 84 can confirm that.

Even a cheap Haynes manual will show you how to check te relay. But you're much better off to buy the factory service manuals....check ebay for them.

I'm not sure the ALDL is the same as an 86 and newer, so you'll want to confirm that also, if it is you can simply run a wire from the positive terminal of the battery to terminal G on the ALDL, that will skip the fuel pump circuit and provide power directly to the fuel pump, if the pump is good it will run continously until the wire is disconnected.

ONCE AGAIN, see if someone with an 84 can confirm what I've stated...mines an 87.

PS. if your turn the key to the on position do you hear the pump run for a few seconds?

 

How loud is the fuel pump supposed to be? When I stick my head underneath the gas tank and my wife cranks the car I hear something but I don't know if its the pump or my antenna motor. And I have a shop manual that I've been pouring over for the past two months and it does mention an ALDL switch but I'm a little confused over where its located.

 

Turn off the radio
The ALDL is not a switch, it's a testing connector it's located on the bolster just above your right knee sitting in the car
http://www.corvettebuyers.com/c4vettes/codes.htm

 

You just don't want to listen to experienced mechanics' advice on the procedure to find out why your engine won't start. If you will measure the fuel pressure, then you will know with certainty that the fuel pump is working. The fact that you can hear the fuel pump run does not mean you have fuel pressure. Several forum members have given you good advice on how to go about finding the cause of your engine not starting, now use their advice!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Its not that I'm not wanting to take their advise, its that I live in one place and the cars stored at another place. I usually only have time to work on it on the weekends and I spend all week getting the parts and tools that I will need to work on it with. I just bought a fuel pressure tester on monday and found my long-lost compression tester last night as well as my test light. I will be working on my car on saturday and will post the results after I get finished.

 

Spot on.

In fact, about 3 years ago, my 84 had to be flatbedded back to my house. The car would start, run up to about 1300 RPM, and sputter. I could get about 15 MPH out of it. Being about 25 miles from home, I gave up and called a tow truck.

The fuel pump was running fine. Powered on for 2 seconds at key on, ran at engine crank and while engine running, and ran full time with 12V applied to terminal G on the ALDL. It was putting out sufficient flow to create about 5 psi, confirmed by my gauge.....and clamping off the return line and bypassing the filter changed nothing. No broken pulsator either.

A trip to the parts store for a new pump, and 30 minutes later it was running fine.

The moral of the story (I tend to ramble...sorry)...is to troubleshoot. Putting your ear to the tank while someone cranks the car will get you....well, dirty.

I'm not trying to be mean...really. I'm trying to help. Hook up a gauge to the pressure side, and run 12V to terminal G of the ALDL. If you have a fuel delivery problem up to the injectors, it will become apparent very quickly.

Keep us advised. If you lived within 20 miles, I'd have your car running this afternoon for the cost of parts and a case of Heineken.

 

Two minor points....(assuming his car is stock)

He has an 84, so should have between 9-13 psi of fuel pressure. And on the TBI system, fuel pressure will bleed off within about 3 seconds of the fuel pump being shut off. It uses a simple bypass style regulator, and doesn't hold pressure at key off like a TPI system would. A leaky injector is extremely easy to diagnose on a Crossfire....you will be able to physically SEE it leaking. One of the few advantages TBI has over later systems is simplicity.

 

Yes, it does.


Correct again. It will run. That doesn't, however, mean the pump is good. A fuel pressure test will confirm if it is healthy or potentially infirm.

 

Well, fellas, I got over here to work on my vette today and I have compression to my spark plugs. What I don't have however, is fuel...I hooked up my fuel gauge, emptying out my fuel line, had someone start the car while I was underneath watching the gauge, and attempting to start the car, the needle of the gauge comfirmed my fears...it stayed at zero. I thought I might have had the gauge on backwards, but when I took it off there was no gas draining out of the line this time. Which probably means I'm going to have to drop the gas tank...Boo! I really didn't want to do that. But you gotta do what you gotta do.

 

Why are you going to drop the gas tank?

 

The internal fuel pump is replaced from on top.