Low Fuel Pressure

[johnnymac09]

Hey Guys,

I have installed a new/used 2.9L in my truck and I can't get it to start. I have been working through a few problems and have got it to the point where when I first turn the key it will bump like it wants to start but won't. I have checked the fuel pressure at the fuel rail and with KOEO I only get 10-15PSI, according to the Haynes manual it should be 40PSI. I have replaced the FPR, Fuel relay and fuel filter. I can hear the fuel pump come on when I turn the key. The truck is an 89, so it only has the one fuel pump in the tank. What are the chances the pump could be only partially working? Is there a way to test it to know for sure it is the problem? The new pump is expensive and I don't mind paying for it if it fixes the problem but don't want to waste money.

Thanks

 

[wstafford]

You can test your regulator by connecting you gauge and pinching off your return line if the fuel pressure rises your pump is good and your regulator is bad. Don't let the pressure build up to high though or you could damage the line in the tank. Hope this helps

 

[johnnymac09]

Does anybody know the correct amount of voltage I should have at the fuel pump? KOEO I get about 4.5 volts on the yellow wire and the pink/black stripe. I think those were the colors.

 

[hidesertrat]

I would go with what wstafford said. It will tell you if the pump is working and if the regulator is good. You may have a bad regulator.

I would assume you would have 12V at the pump, but than it would only be there when the pump is running. Not sure why you would be getting 4.5 volts, but if the pump isn't running when you measure the voltage, it doesn't count.

 

[johnnymac09]

You can test your regulator by connecting you gauge and pinching off your return line if the fuel pressure rises your pump is good and your regulator is bad. Don't let the pressure build up to high though or you could damage the line in the tank. Hope this helps

Thanks for the info, I have replaced the regulator already, but I ran the test anyways, because you just never know. I pinched off the line and the pressure did not rise.

I would go with what wstafford said. It will tell you if the pump is working and if the regulator is good. You may have a bad regulator.

I would assume you would have 12V at the pump, but than it would only be there when the pump is running. Not sure why you would be getting 4.5 volts, but if the pump isn't running when you measure the voltage, it doesn't count.

You are right the 4.5 was a bogus reading. I re-tested with the pump on and got 11.6V, that is pretty good considering my battery was down to 11.7 after all the the attempts to start.

I found this troubleshooting checklist and figured I would post it in case anybody else needs it. I have run through the list and it looks like I am buying a new pump tomorrow, I will let you know how it works.

http://arrc.epnet.com/autoapp/8967/chiltonimages/8968/89685g16L.gif

 

[hidesertrat]

You still may have a chance of not having to spend any money...you pump may be partly clogged and not able to draw enough fuel to build the pressure. I would get the new pump, just in case, but be sure you can return it if you decide you don't need it.

I work on a old dodge and the pump didn't work at all. Took it out of the tank, it wasn't even turning. Cleaned it up, lubed it with WD-40 to get it to turn. Put it back in and the car has been on the road for the last year. The lady was happy not to have to spend the 150 for a new pump.

Just a thought..........good luck.

 

[johnnymac09]

You still may have a chance of not having to spend any money...you pump may be partly clogged and not able to draw enough fuel to build the pressure. I would get the new pump, just in case, but be sure you can return it if you decide you don't need it.

I work on a old dodge and the pump didn't work at all. Took it out of the tank, it wasn't even turning. Cleaned it up, lubed it with WD-40 to get it to turn. Put it back in and the car has been on the road for the last year. The lady was happy not to have to spend the 150 for a new pump.

Just a thought..........good luck.

That is a great tip, too bad I didn't see that before I changed the pump. No matter, the pump is in, and I am getting the 40PSI I should. The truck still isn't starting, but at least I am over that hurdle. Now I have to go back to square one and start checking for the next problem. I am hoping it is just a matter of getting the distributor in the right spot.