I have an 85 that will not start. If i spray a little starting fluid into the intake it will run until it burns the starting fluid up. I need a little guidance as to what to look for and where to start trouble shooting from here. I am thinking the fuel punp is a good place to start. Shouldnt i be hearing the pump run when i turn the ignition to the on position? ....

 

Yes, for 2 seconds at key on. Then the ECM will shut it off unless it detects that you are cranking the car.

OK, you're on the right path, so let's troubleshoot this puppy and get it running again. Put a fuel pressure guage on the schrader valve on the fuel rail. Turn the key on without trying to start....tell me what happens. You should get about 38-44 psi, and it should hold that pressure for several minutes after the ECM powers off the pump. If pressure, does it hold? If you have pressure and it holds, there is another issue, and we will tackle that separately.

If no pressure, run 12V from the battery to terminal G on the ALDL connector....this will energize the pump full time without regard to key position. Pressure? How much?

If no (or low) pressure, pinch off the fuel return line with a pair of vice grips and run the test again. Pressure now? How much? If you previously had no or little pressure, and it suddenly spikes with the return line pinched off, replace the fuel pressure regulator.

If still no pressure, remove your gas filler door and rubber boot. With terminal G still energized, test for voltage in the harness. If you have 12V and can hear the pump run, remove the pump assembly and check for split pulsator. If the pump runs but doesn't produce enough flow to create pressure on the fuel rail, and nothing is split or broken, replace the pump and filter sock. If you have 12V and cannot hear the pump run, remove it and check for broken or corroded connections. If all connections are good, replace pump.

If you don't have 12V with terminal G energized, correct the open circuit. You will need the factory service manual to trace the circuit by wire color.

There you go....fuel system 101 class is complete. Run the tests and tell me what you find. Happy wrenching.

 

nice work, frizle! easy to follow and it makes perfect sense!
well done!

I assume an '84 would use that procedure as well? terminal 'g' for the pump? the harness you refer to is under the fuel door boot?

 

Something i should ad that might factor in here. I bought the car as a winter project and it hasn't been taken care oF AT All. Anyway's the security system has been removed from the car. Would that have anything to do with the operation of the fuel pump?

 

The security system would only disable the starter. It would have no bearing on the fuel pump unless someone has "re-engineered" the system somehow.

Thanks. Yes, terminal G energizes the fuel pump on the 84 as well. The procedure does differ somewhat on a crossfire system though. Here are the primary differences;

1. Fuel Pressure Regulator. A TPI car should hold most of its fuel pressure for several minutes after key off. The Crossfire will bleed down to zero in seconds. This is normal. The TBI has a flow through regulator....essentially a metered leak....into the return line.

2. Schrader Valve. The 84 doesn't have one, so you have to rig something up to test pressure. The manual calls for a T fitting to be mounted between the throttle bodies using a special test pipe...which I've never been able to locate. I removed the crossover pipe between the TBI's and had a hose and tube shop fab up a test port with a male fitting on my pipe....and crimp on a corresponding female fitting on my low pressure guage. Here's what it looks like.



....and in use...



The best $25 I ever spent on the car. Makes life easier for us CFI owners.

3. Fuel pressure. The TPI system should have between 38-44 psi, the Crossfire between 9-13 psi.

Those are the fundamental differences. The rest of it is pretty much the same. Hope this helps.

Oh...almost forgot...the wiring harness. It is located just below the rubber boot under your fuel filler door. A pic is worth 946 words.

 

um, I'd raise the pic to an even 1k! sez it all.

love that fuel feed pipe with the port!

frizle, you're the man! thanks for directions! the fsm is great but this forum is where the blanks get filled in!

thank you!

 

Frize, I looked all over this motor and this is the only thing i found that looks like a schrader valve is this right?

 

yep that's it...


There are a few more questions you need to answer before I can tell you where to go from here.

Check engine light stay on (koeo)?

Any check engine code's

Oil level correct?

When your ready and can answer those questions, I can help you more.


Btw I have the entire wiring diagram for your car if you need it.

 

It can run, but it can't hide. You found it.

 

I'll bet it has nothing to do with the fuel pump. That it's really the ECM Coolant Sensor!

 

^^^CRACK is not your friend^^^

 

Here we go again....let the guess-a-thon commence. After all, troubleshooting is such a waste of time right?

Hell, let's take it to the next step even....just start buying parts like mad and replacing everything until it runs....after all, it's only money, right? And hey....time has no value either.

How in God's name do we determine if the fuel system is healthy or not until we....oh I dunno....TEST IT MAYBE?

Please tell me you're not a doctor....I'd hate to go in and say "Doc, I have a pain in my chest" and wind up having my left leg amputated because nobody felt like running tests....

Sheesh....

 

If you do buy a fuel pressure gauge, do yourself a favor and buy quality. It also helps if it has a 45 degree connector.
I bought mine on the cheap and it told me I had 20psi which cost me another $80 for a fuel pump I really didn't need.

 

Listen to Frizlefrak, he is leading you in the correct direction. Test before you start throwing money at parts than may not solve the problem. You might be able to rent a fuel pressure gauge from one of the parts stores near you. They run 40-60 dollars depending on where you buy one. It would also help you tune the car in the future.

 

The amount of HORRIDLY BAD ADVICE on this forum grows larger every day.

And I agree 100% with Frizlefrack.....most users here are way to eager to blindly throw parts at a problem rather than spend a little time and effort diagnosing the issue to see just what the problem really is.

 

Frizle, I haven't bought a manual yet and not real familiar with everything on my car yet. Can you show me a picture of the aldl connecter and which one is terminal G.

 

I found the ALDL connector and the terminal G. I have ran all the tests and have 0 psi on all checks. I do get 12 volts at the pump connector with terminal G energized but do not hear the pump running when it is connected.I stopped at this point. I am going to remove the pump tomorrow and see what it looks like and go from there.

Thanks for the help so far...David

 

Some tips
http://forums.corvetteforum.com/c4-t...h-article.html

 

David....I have a pic of the ALDL, but doesn't sound like you need it after all. Sorry, was out of town with no wifi for a couple of days.

Sounds like it's time to pull the pump out. One of the real advantages of C4 ownership is that the pump comes out from the top. You won't even get the first beer finished before it's sitting on the bench.

If none of the connectors are corroded or broken, you have a dead pump. With terminal G energized, you would be able to hear it at the filler area. Sounds like you did a good job of troubleshooting it.

 

I had the same problem with my 84. After much troubleshooting and replacing the computer (I now have an extra if anyone needs one) I found the fuel pump relay was bad. It's located on the firewall to the left (facing the firewall) and below the power steering unit.

Good luck,
Rich