AQWIKZ

I was driving home yesterday and all was good then all of a sudden
no power and car shut down. there are no codes on DTC. I got the car towed home first thing I checked was fuel pressure. a big fat zero.
I did not here the pump run,checked fuse 13 and that is good. what else should I be looking for? fuel filter was changed in october.

thanks everyone in advance

dgrant3830

I agree. That's the first thing I thought of as well and we've heard of that relay failing before on more than one thread. There's also been several cases of the fuel pump ground coming lose.

pewter99

unlikely it is bad but you can swap it out quickly with another one under there to see if the fuel pump fires up....you may also want to check the ground back there on the rail it may have come loose

pewter99

yeah I had an intermittent fuel pump issue and swapped the relays and it would work for awhile then we thought perhaps we had a bad fuel pump...swapped it and still had an issue ....once... checked everything wiring wise...no clue... if it happens I just wait after the car sits for 20 minutes it will start like nothing happened...may not happen again for 6 months

dougbfresh

Many times a fuel pump will seize up when it gets too hot, after it cools it will run again-generally impending doom for the pump.

AQWIKZ

I will double check all grounds and the relay when I get home. I did try starting again this morning before work same thing. zero pressure and no pump

pewter99

mine did it hot or cold...didn't discriminate ...I hate intermittent issues

mundo

I was working on Mikes car this morning. I shorted across the reed part of relay 35 and the fuel pump started. The coil part of relay 35 doesn't have voltage. It comes from something in the manual called the fuel pump control module. Schematic wise it looks like a switch and supplies 12v to the coil side of the relay. Anyone know where this is at?

lucky131969

Not sure what manual you are looking in, because no such animal exists. The PCM supplies 12 volts to the coil of relay 35, and the coil ground is provided from SP122, which is in turn grounded at G105.

http://forums.corvetteforum.com/1574199890-post2.html

mundo

There is no voltage on terminal 85 of relay 35. I know the 12 volts supplied to the coil comes from the PCM. I shorted terminals 30 to 87 with a paper clip and the car started and ran. Assuming the PCM is good, what in the car can keep 12 volts from the coil of relay 35. Could it be theft detererrent? What are all the conditions that could turn the fuel off?

lucky131969

If you are saying there is no voltage on 85 (as labeled in my pic)....that's good. That is the ground. 12 volts is supplied on 86(as labeled in my pic).

No, the theft deterrent does not control the fuel pump, just the fuel injectors.

mundo

I stand corrected. The reality is there is no voltage at the coil of relay 35. Without voltage at the coil the reed of the relay will never close.

Assuming the PCM is good, what are all the conditions the PCM would not let voltage to the coil of the relay? We did not remove and clean the connectors directly on the PCM. Hard to get to. We did remove and clean the contacts of the three round connectors going to the under hood fuse box from the PCM. We use electrical spray contact cleaner on both male and female ends. As I stated earlier I shorted with a paper clip across terminals 30 and 87 of relay 35 and the car started and ran OK. Can't leave it that way. We suspect the PCM is good and is not allowing the car to start for some reason. A few days ago the alarm went off with beeping horn. The FOB hasn't worked in years. Any advice is appreciated.

lucky131969

Ok, trying to help here.....

I don't know what "I stand corrected" means. Does that mean you verified you have a good ground on 85(as labeled in the pic)? Hopefully, you are using a meter to do the testing.

The fuel pump will only have 12 volts at the connector for 2 seconds when the key is turned to on. If the motor does not crank, or start, there is no output from the crankshaft sensor to the PCM, and it will not allow the fuel pump relay to stay engaged....so the voltage at the pump drops out.

Again, the theft deterrent has NOTHING to do with the fuel pump, just the injectors. The fact that the car runs, with the relay socket jumpered, tells you the theft deterrent is normal.

So if you are certain, that you do not have 12 volts (key on or cranking) at 86 (as in my pic), then you either have one of two conditions:

1) Open circuit between the fusebox and the PCM connector
2) Bad PCM

Virtually all of the issues with the fuel pump relay I have seen(or worked on), have been due to no ground at 85, due to corrosion at splice pack 122, which is located under the battery tray.

Good luck.

mundo

I do not have 12v at 86. I'm certain. Hope its not the PCM.

mundo

Lucky, the diagram you sent me must have been for other than a '99 corvette. In the '99 corvette shop manual terminal 85 of relay 35 is the voltage side of the relay. Terminal 86 is the ground side. The PCM works OK. Putting a voltage indicator light on terminal 85 after the car is turned on (not started) the voltage comes on for 2 seconds then goes away. After stating the car the voltage stays on while the engne is running. You were right about one thing. It's a ground problem. Measuring with an ohm meter terminal 86 to GND is very high resistance.

I took the battery and battery plate out. I noticed a ground distribution terminal where the wires come out of a big cable. Normally this terminal connects to a bolt in chassis ground. I don't see that. I do see two thick ground wires coming out of the fuse box to a chassis ground lug. Which one do you think is the culprit?

AQWIKZ

I want to thank lucky131969 and mundo, between the two it was determined to be a ground G105, the small ground from wire harness that I forgot to hook up. the forum is great.

lucky131969

Well, done. Mundo told me about the exhaust swap. If you disconnected the ground above the starter (G106), it might be worth checking....to make sure it's tight.

mundo

Thanks Lucky. It was a connection at G105 we missed. Thanks for the call and the advise. We connected up G105 and it worked great - Thanks!

lucky131969

butch353

i had no starts an elve. cooling temps on my 09 0felt the power box on the right side of engine it was warm. started car an ran a while took a temp reading with the infer red relay 35 &55 where hot. took to dealer under warranty. Had to replace power box as contacts for relays where loose. cleared up everything happy camper. this Z 06 had the engine replaced at 9000 has 45000 on it now so think when it was changed they didn't get the box back. on right. have extended wart.on it