Starting to troubleshoot Jen's vette today, fun fun. So where is the fuel pump relay on an 87? Is it up under the dash on the drivers side like the 90 or what? Also do the 87's have a seperate little fuse cluster under the dash on the passenger side like the 90's do as well.

I think I have finally gotten the wiring mess all straightened out under the dash so I can actually troubleshoot problems like normal now. We shall see. Any help on the relay location is appreciated. Also where is the fuel pump specific fuse located. I don't have a FSM for her car, I have them for 90, 91, ZR1 supplement and 94. Nothing for the 87 yet.

Thanks!

 

The fp relay is next to the wiper motor on an 87, the fuses are in the fuse panel accessible when you open the passenger door. There is also a fusible link to the fuel pump relay...don't worry about that now, if you turn the key to the on position you should be able to hear the relay activate the FP for a few seconds, if the relay goes bad the oil pressure switch will activate the FP after oilm pressure reaches 4 pounds.

 

Rick thanks for the response. Let me give a little more background on the problem. One day the wife goes out to start the car and it does nothing, no crank, no start nothing (not sure if the FP was priming because I was not there) So I go out to check it later that day after she went to work in another vehicle. I get out there and it starts fine. I drive it all day and start it multiple times without fail. She gets home from work and I tell her to come here and look at the car, she gets in the garage and it cranks but will not start. I continues to do this for the rest of that day. I was kind of busy so I didn't look into anything. Next day I went out to the garage to investigate and now it does not crank or anything. No FP prime no nothing. Battery is fine, dash lights up fine, I hear some relays or something in the dash clicking when I try to crank it but thats about it. All of this was 6 months ago. So upon further investigation I discover that the previous owner did a hack job on installing an alarm that had its hands into everything including remote start. So I begin removing all of that mess so I can troubleshoot it like a normal problem and rule out the alarm having conflicts with normal systems. Not to mention I dislike alarms on C4's anyway. So thats where I am now. No crank, no start, and no fuel pressure. I figured I would check the relay to see if it was getting voltage. Not sure if there are 2 problems here or just one all inclusive one? Any suggestions.

Lee

 

sounds more like a VATs problem, could be the key pellet, ignition switch or you may need to bypass the starter interupt relay (VATs) that might be the VATs relay clicking you're hearing behind the center console, do a search here..VATS, there have been several postings and jfb usually responds with an easy method of bypassing it, just installing a simple Radio shack resistor with the same resistance as the key pellet, I just can't remember which 2 wires they are that come out of the steering column. If you can't find any info...post something like this "could this be VATs?" in the tech section.

 

Good clean, tight battery and starter connections ??
Heres some info on your VATS
http://members.shaw.ca/agent86/Vats%20Electrical.pdf

 

Lee,

You can hotwire the fuel pump from the diagnostic port. Of course right now I can't remember what pins to jump together. That should at least tell you if the relay works. The relay yes is on the firewall by the wiper motor. The wire insulation shrinks back over time so it may be worth investigating. On the 4+3 cars you can swap the relays to test because they are identical and right next to each other.

I kind of look at it like the MAF relays, if you can't remember when it was changed, then change it.

Its too bad it won't crank now, because once you get over a certain PSI of oil pressure the other fuel pump power source would kick in.

 

hot wiring the fuel pump scorp talked about is done like this...a wire can be ran from the positive post on the battery to the ALDL the bottom pin on the left, that will bypass the relay and switch and power the fuel pump...but it won't do anything for the no crank problem.

 

Ok, I bypassed the VATS relay behind the DIC as per instructions found on forum member GIJoes page. I also placed the proper resistor in line with the key cylinder wires as per same instructions. I still have the same no crank, no fuel pressure problem. Only now I don't hear the resistor behind the DIC clicking since it's bypassed? So my question is: Does the VATS fuel enable signal to the ECM also regulate the engine cranking over as well? If it only stops fuel I have no clue what the problem is since I still have 2 problems, but if it stops both engine crank and fuel pump enable that may be the culprit? Any more suggestions?

Lee

 

Test the relay for 12 volts when the key is on. If there is no 12 volts, I think your problem is a burnt fusable link on the junction block located next to the battery.
This sudden loss of power that effects nore than one circuit is usually traced to one of the fusable wire links being burnt out. Most of these feed more than one fuse in the fusebox.
The fact that you had power intermittantly also tends to point to one of these links. With the low amperage draw necessary to power releys, the wire can vibrate to where the burnt ends inside the wire can tough and allow enough current to work intermittantly. as it is only needed to activate the relay during starting it can reopen while driving resulting in no start once it is shut off.
If the burnt wire is not visible right away, You really have to take them all off and pull on each one to see if the wire cover stretches or not. They are all the same color so you have no way of looking at them and telling which one is for the fuel pump relay. Do not forget to clean them all up with sandpaper and coat with dielectric before reinstalling.
You can buy the replacement fusable from NAPA and saulder it in if this is the problem.

A word of caution, count the number of wires you take off as they are very short and you can lose one in the mess if you are not carefull.

Hope this helps.

 

Ok after more investigation, I found that there is infact voltage to the fuel pump when I turn on the key to prime the pump but only for a 2-3 second time, but the pump does not run. I can't hear it and there is no pressure on the manual gauge that I have hooked to the shraeder valve. There is also constant voltage to the fuel pump when I jump from the battery to the ALDL connector. But again, no pump running and no fuel pressure as indicated on the gauge. So for sure the fuel pump is bad, now I just need to figure out why it's not cranking. There is nothing. No change in voltage when I hit the key, no solenoid noises nothing. Is there a fusible link related to that?

Lee

 

http://members.shaw.ca/agent86/Power%20Distribution.pdf
http://members.shaw.ca/agent86/Start...g%20System.pdf

 

The fuel pump is only supposed to run for a few seconds to prime the system. No fuel pressure could be anything from a dirty sock, clogged inline filter or the pump itself. You can pull the pump and bench check it with 12 volts to see if it's actually pumping. Fuel pump removal isn't difficult at all and it would seem the best place to start. I believe you are looking at two problems though but until you can verify fuel pressure, we're spinning our wheels.
Another thing to consider, and I'm sure others can chime in here is the Oil pump. I could be wrong but the ECM must sense oil pressure before sending fuel to the engine. I'll check my 88 manual and see what I can come up with.

 

This is a common misconception. The oil pressure switch is an alternative power source for the fuel pump. When the switch sees over a certain PSI (its low, can't remember what) it sends power to the fuel pump bypassing the fuel pump relay. If your fuel pump relay were to fail while driving, this will keep you running.

Your fuel pump will keep feeding the engine even at 0 oil PSI, you probaby don't want to ask me how I know.

 

Bench test the fuel pump and replace if faulty. Check the connections on the starter and solenoid. Clean the pellet on the key with alcohol or try a spare key. Check all the fuses by the passenger side door and there are a few behind the DIC. Check the fusible links.

 

Here is the fuel pump relay location for future use.

 

Here's a few things for you.

If you're hearing a noise for 2-3 seconds, that is the fuel pump running.The relay when energized triggers the fuel pump to prime the system for 2-3 seconds. And the ignition key when turned off and then on again will not prime the system again for something like 10 seconds after the key is off...then turned back on.

Yes, there is a fusible link, from the power tower behind the battery, one fusible link leads to the FP relay, just before the relay it branches off and also feeds the oil pressure switch. That's all that one fusible link feeds. If you're not getting fuel to the rail it's either a plugged fuel filter, kink in the line or a bad fuel pump.

But you have 2 problems here...none of the above will prevent the engine from cranking. Before you go off into to many directions check all related fuses in the fuse panel.

I think you should focus on the crank issue first, and you could pull the fuel feed line off at the tank location under the fuel door, connect a piece of fuel line directed into a container, without having to pull the fuel pump, turn the key to the on position and see if your getting fuel.

 

I just fired up the heater in the garage so I will be back out there for a few hours this afternoon. Going to focus on getting the car to crank over. I suppose I will start with the starter itself. Who knows, it may actually be a normal problem for once, but I seriously doubt it.

Lee

 

Ok, after all that mess it ended up being the stupid starter is bad. So I have 2 seperate problems that surfaced at the same time. Starter and fuel pump. I checked all the connections on the starter then decided to hit it with a hammer. I get in the car and I turn the key, it made just an ever so slight noise for a split second. So I went back under and hit it again. This time I turned the key and it turned over fine. I then bench tested the FP and it's dead. So I just ordered a new pump from Racetronix and I will get a starter here locally. Stupid car. At least now I can see a faint light at the end of the tunnel now. Thanks for all the help and suggestions. Although not too bad for the original 1987 starter with over 200,000 miles and same for the fuel pump. Neither one have ever been replaced.

Lee

 

Congrats .... one step at a time will get you there every time

 

Firstly I appoligse for the hi-jack, but it seems you guys could help answer a question for me.

My oil pressure switch is leaking I belive. No where above it is wet, and it seems to be above the pressure guage sender. Unfortunately I don't have access to one on the shelf in the UK to try it.

My question...

Can I disconnect the switch, screw in a blank and get the engine running? It sounds like this pressure switch is not essential for running, or even very usefull for that matter.

Thanks in advance