85 C4

Cant get it to start.
I had a no crank no start situation initially until I jumped the Fuel pump interruption relay

Now crank and no start
It has a new fuel pump and filter
Fuel squirts out of the fuel fill line to the fluid pressure regulator strongly when disconnected.
When that line is plugged in however, fuel pressure at the schrader valve on the rail is 0
The crank is strong, battery is new

Is this still the VATS?
I thought that since it went from no crank to crank that i had bypassed this. Is this wrong?
Why is the fuel pressure still 0?
Is it the FPR?
Is it the rail?

Charles

 

Since you are getting fuel to the regulator you should get some sort of pressure reading at the Schrader valve on the fuel rail. Either the pressure regulator is completely shot and is letting fuel simply return to the tank without holding it back and pressurizing the rail. The fuel is going somewhere. Has this car ever run under your ownership? If so, when did the no crank/no start situation begin? Pull a few easy to get to spark plugs, what shape are they in?

 

You can test the fuel pressure by pinching off the return line at the fuel tank. It's easy to get to. Just pinch it off with a pair of vice grips then cycle the fuel pump and see if you get pressure. If you do then look at the regulator. If you don't then look at the pump or for a clogged fuel filter. Have you checked for spark?

 

I have had the car for a few weeks. Initially it was a no crank no start, now only a no start with a good crank. The FPR is original. The spark plugs have spark and are new. I put them in. By your scenario, this implicates the FPR as the problem?

C

 

I can do this. The Fuel pump is new, I put it in. As I said, the fuel line to the FPR definitely squirts out fuel. The filter is also new. I put it in as well. There is spark.

C

 

@slow-vette has the right idea. Pinching the return back at the tank creates an artificial pressure regulator and should allow you to see some pressure on your fuel pressure gauge while connected to the rail. I asked about the spark plugs because you might but highly unlikely have some injectors leaking and pouring gas in to the cylinders thus not producing any pressure. Yes, you can replace the FPR but the upper TPI intake has to come off. Look forward to hearing your results after pinching the return line.

 

Yes, I saw a video or two about how to tip up the plenum to get to the FPR. It does not seem hard even for a newby like me to get done. It seems as though a consensus on the forum is suspicious of the FPR. I will probably get the new FPR tomorrow and work on it this week.

C

 

I'd still check the HEI module, even after you sort out your fuel delivery problem.

Good luck with it.

 

Before you pull the FPR - check that your fuel pressure gauge is working... First off - do you have another car (say a Daily Driver) you can try it on ? I've seen a case where a "inexpensive" (read Harbor Freight) fuel pressure tester did not screw onto the "port" far enough to depress the schrader valve. Thus no pressure reading EVER

The idea of pinching off the return line is the normal test protocol - another one is to have someone turn the Ignition on (thus energisin the fuel pump for about 2 sec, while you manually depress the "pin" on the schrader valve on the fuel pressure test port - at least some gas should squirt out.

 

Yes, I did test the gauge on another car that runs and it registered pressure. I sprayed WD40 on the schrader valve and made sure that the pin depresses. I can check depressing it while cranking as well.

C

 

Welcome to the Corvette Forum Charles212! We are glad you are here! This is THE place to go when you have questions about a Corvette!

This might seem like a "strange" test to perform but please try it just to be sure.

Measure the Battery Voltage at the Battery and then right away measure the voltage supplied to the Fuses. It should be the same or very close to the same voltage. I once saw a C4 with corrosion on a post that caused a voltage drop of close to 2 volts inside the Corvette. Nothing worked right until the little post is cleaned off and the connectors as well. The Post I refer to is where the Fusible links connect to the Battery Positive Power, I don't know where it would be on the 1985 C4 but on my 1988 C4 it is behind the battery under the side cover. It has a red wire going to it directly from the battery Positive terminal. On my C4 it supplies 7 fusible Links with 12 Vdc power which then goes to the fuses and to the individual components. Having full voltage is really important to a C4 so this test is important.

Another good test is to put 12 Vdc to the Electric Fuel Pump and see how it works. Then follow the wiring backwards to find the issue and solve the problem. Remember that a dirty fuel filter can slow the fuel down a bit as well. If Ethanol sits inside the fuel lines it can cause them to rust shut internally. That happened to my C4 as a matter of fact.

If you wait a bit we have several 1985 experts here on this forum, one is bound to check in before too long.

 

Great points. The filter and pump are working well. I am hoping I am missing something simple and can find it.

C

 

In regards to lack of fuel pressure, I was able to advance a thin but stiff wire up the pipe between the fuel line fitting to near the FPR. In addition, the wire came back wet and smelled like gas. I am taking that to mean that that that line is open to the FPR. I am becoming suspicious that my Schrader valve does not work and therefore is not demonstrating a pressure on the pressure gauge. The next structure in the sequence is the FPR. Does replacing this at this point make sense?

 

Welcome Charles212 to the joy of C4 ownership...
Since this 85 is new to you I highly recommend you change cap, rotor, spark plugs, spark plug wires, pcv valve, air filter, oil, oil filter unless you have receipts from previous owner this was done recently. .Also, please check the battery as ctmccloskey suggests....... You mentioned VATS in your first post. You don't have VATS. VATS did not come until 86. In fact, I prefer my 85 over my 88 due to the lack of gadgets to mess with. (VATS, ABS, Electronic HVAC control, third brake light did not come until 86.) You will have to deal with the headlight motors and electronic dash at some point, but there are fixes for these that are not too bad........One question. How old is the fuel in your 85? Bad gas will not help your situation.

 

Thanks for your thorough post. All of t his is very new to me.

I have replaced the coil, plugs, air filter, oil, oil filter and ECM. I drained the fuel and put in new gas.

I was told the ECM was good to go and was essentially plug and play. There is spark. We checked the cap and rotor and the timing as well. There is a small amount of self made wiring that is present but I do not think it is of concern to make the engine run. I can post a picture.


Ok, NO VATS, thats good.

I am going to check the ohms on each injector and i have ordered a noid light for injector pulse. I am not sure if the Schrader valve works and may be giving me falsely low readings. I made sure that the gauge works on another car.

If my injectors and pulse show to be normal, I am going to replace the FPR.

Question: What are the correct fuses for the fuel injectors. I am seeing conflicting information. There is a fuse diagram on the forum here, but it doesn't match up to what is in the car.
With what I have said, does this seem reasonable? If not, please teach me what I need to know.

C

 

You have done a lot of good work on your new to you 85. I would check your injectors next. I bought a Kent Moore fuel injector tester kit, but I have not needed to use it yet. It seems easy to test them; so once you get the tools, just follow the instructions. I have not had issues with my injectors but I know that there is an issue with ethanol fuel harming the seals on the early stock C4 injectors. If you do not have a 1985 Factory Service Manual, you need to buy one. Ebay has them listed all the time for less than $100. Well worth the money. I posted the pages from the FSM on the injector wiring.

 

Thanks much. I will test the ohms on the injectors and use a noid light to check pulse. If they check out Ill go after the FPR.

C

 

So, all my injectors have an ohm reading in the low 16s. I think this is healthy. I am about to make the plunge to get a new FPR, what does anyone think given the direction of this thread?

C

 

I think that changing out the FPR is a very reasonable idea based on what you've posted so far.

One other thing to consider ... The schrader valve on the pressure test port unscrews - just like the schrader valve on a tire does (same tool and everything). So - if you think it might not be working - you could simply remove the valve, install the fuel pressure gauge, and check fuel pressure by running the pump. Just remember to reinstall the valve after the test ....

 

Thanks much Purple. Would it be worthwhile to get an OBDI and see if there are any codes with the key in the on position. Are there any security anti theft issues that could be in the way as well for the 85?

Are you talking about the entire shrader valve of jus the innards?

C