Fuel Pump Not Working

[Keyav8r]

I installed a new Bosch fuel pump 2 weeks back but didn't have time to put fuel in the tank and try to start the truck. I did cycle the key on to check if my sending unit was working and don't remember hearing the pump run.

Put about 4 gallons in the tank today, turned the key, no fuel pump noise, fast crank, no start (however, the gauge did register correctly).

Tapped an AC hose to the fuel rail, turned the key, fast crank, no fuel from the hose.

Disconnected the fuel pump connector to check for voltage to the pump and got an intermittent 8 to 12 volt reading when cranking the engine.

Tried swapping relays to see if that helped, but nothing changed.

Any ideas of what to,look for?

Could I have fried the new pump by letting it run dry?

Planning on pulling the pump again next long weekend (2 weeks from now). May try to bench run it just to be sure it works.

[DirtyComanche]

Sounds like DOA pump.

 

Pull it back out and make sure the connections are good.  Try driving it with a battery/leads out of the truck, but if you have voltage while cranking (8v is reasonable because of starter draw) the problem should not be with the truck's wiring (unless it is phantom voltage, which you could rule out by putting a light bulb across the pins or using a test light).

 

They can run dry for a long time before overheating.

[Keyav8r]

Thanks, that confirms my plans. I still have the old pump, which was working when I pulled it to change the sending unit. Hindsight being 20/20, I should have left it alone. But, I thought why not change it while I have it out.

[DirtyComanche]

As long as you lubed the o-ring when you installed the sending unit, it's about a 10 minute job to pull the pump...

 

 

Not that I have any sort of leg to stand on when it comes to telling people that they should work on their junk.

[Keyav8r]

Somehow, for me, those 10 minute jobs turn into marathons. But, it has to be done. Hmmm, might do the u-joints while I've got the driveshaft down.

[omega_rugal]

 

They can run dry for a long time before overheating.

 

mine died within 5 minutes of running dry... don`t do it...

[DirtyComanche]

 

 

They can run dry for a long time before overheating.

 

mine died within 5 minutes of running dry... don`t do it...

 

 

That's a long time in terms of not having fuel in the tank...  Since you're not going anywhere at that point anyways.

[Pete M]

does the pump have ground?  voltage is great and all, but it needs ground too. :D  it usually gets its ground from behind the taillight and through the one or 2 connectors between that ground and the pump.  any failure will give a no-start.  I ran a dedicated ground for the pump to the frame close by.

[Keyav8r]

Pete - I'll give the ground a check before pulling the pump. How did you route your dedicated fuel pump ground? Did you ground the tank to the chassis or run it back to the taillight ground?

[Pete M]

directly to the pump's ground wire. 

[Keyav8r]

Problem solved. I used my ohmmeter on the fuel pump and had a good ground but no continuity through the pump. Checked the old pump and had continuity through it. Dropped the driveshaft, pulled the pump and found some dumba$$ had not rechecked the connector on the pump and it was loose. Pushed it firmly back in place and pulled on it to make sure it was tightly in place. Did a quick bench power test and the pump ran.

 

So, I put it back in the tank, turned the key and could hear the pump running. Turned the key to start and after 5 seconds or so the engine fired right up.

 

The DA responsible for this unnecessary rework will remain unidentified in an attempt to retain some dignity.

[johnj92131]

Congratulations!  

 

From this Dumb A$$ and thanks for posting the solution for the next bunch of D.A's