This morning I went out and my truck wouldn't start at all. The engine turns over but it just won't catch. I attached the fuel pressure gauge to the test port on the fuel rail, cranked the engine and got 0 psi pressure. So now I know it's not getting fuel. Now how do I determine if it's the fuel pump or just the fuel pump relay that's bad? Normally I'd just put a new relay in and start from there. Unfortunaletly it appears that the relay is a dealer only part and none of the local dealers can get the relay before next Tuesday. Is there any way to jump out the relay?

Any other possibilities other then the relay or the pump?

It's a 2002 QC 4WD w/5.9L

Thanks for the help,
Peter

 

More than likely it will be the pump or relay. There are a few ways to test the relay but I would have to see the relay and the wiring schematic to tell you how. You can also just jump the relay if you knew which prongs did what on the relay.

Another, way to check if it is the pump is to find the wire that feeds power to the pump. If you have power then the pump is crap. If you don't have power then you would have to proceed to check the relay and wires before the pump. If you have power to the relay but not after then you found your problem.

Also, you should check to see if you have an ASD relay because that could possibly be the cause too. To check that one you can just pull a plug and crank the engine to see if you are getting spark. If you have spark then it's not the ASD relay. Hope that helps a little.

 

If you have fog lights, swap the fog light relay with the fuel pump relay. See if it works. If not then it's probably something else, but just to check try the foglights, if they work, you know the relay was fine. There's better ways to test the relay, butthis works.

 

Right. Thats a good way to troubleshoot to see exactly what the problem is. If its not getting fuel, then your right, it's probalby either the pump or the relay. Swap in another relay for it, and try it then. If it still doesnt work, then you move on to the next possibility. Check your fuel pump. Heres a couple quick steps for you.

Inspect all the fuel lines, make sure there isnt just a break in the lines somewhere.
Set the parking brake and then have someone else turn the key to turn over the truck, while you listen to the fuel pump. You should hear that whirling, whistling sound for a couple seconds.

If you dont hear the noise:
The fuel pump isnt operating. Check the fuel pump circuit, all the related fuses, fuse pump relay (you might need a replacement after all.. but check that first anyway), check the power and the ground to the fuel pump. If its powered and grounded, and circuits are good and so are fuses and relays, and it sitll doesnt operate, replace the fuel pump.

If you do hear the noise:
The only way youd be hearing the fuel pump whining but not getting any fuel is if theres a leak somewhere. Check the pressure again. If nothing, inspect your fuel lines again. If its pumping fuel but your still not getting any pressure, then your missing something. Check the entire length of fuel lines for leaks. If none are found, replace the fuel pump, then try again. If still no go, then replace the fuel pressure regulator and the fuel filter.

Good luck. Keep us posted and we'l be happy to try to help!

 

Well, I swapped the relays around and it was the fuel pump relay that was the culprit. As soon as I changed them the truck fired right up. I ordered a new reay so I'll hgave to wait a few days before the fog light work but that is a small price to pay for the truck to be running.

Thanks to all for the suggestions on trouble shooting this.

Peter

 

some good info to know!!