Low Fuel Pressure

[jeepit]

Can cold weather (-10) affect fuel pressure? Mine has dropped down. Truck starts runs fine.

 

[DavidC]

Yes it can, fuel is a little thicker. I noticed on mine last time it was out, after the fuel warmed up circulating back from the VP it normalized.

 

[jeepit]

Mine didn't change after warm up. I was plowing and I ran over a driveway marker. It flipped up under rear fender where the Airdog is mounted. When I started truck I could hear the pump run. I'll need to check it out tomorrow.

 

[JR]

I would also check the pressure regulator on the Air Dog (spring and ball)

 

[jeepit]

No power to pump. Where should I start trouble shooting and in what order?

 

[DavidC]

Not sure what has been done. The usual for a relocated pump is to install a remote relay and wire the coil to the OEM harness which comes from the ECM. That part energizes the relay. Next is to run a wire and remote fuse to the relay common terminal then from the normally open contact on relay to pump.

 

[DavidC]

The fused wire is usually wired to the battery and fuse should be nearby. Relay is mounted to firewall or some attach to PDC lid.

 

[JR]

Definitely should have a spare relay on hand for that. I always carried one in my glove box just in case.

 

[Chief USA]

Be mindful of if and when you DO get power to the pump to carefully observe if the pump is actually moving fuel or loading down with resistance. It would not be the first time in these really cold conditions that a water separating filter froze or water somewhere in the system between the tank and the injector pump froze and blocked fuel from passing. Sometimes you may have to push the truck into a heated garage or shop if you have one available or just wait for warmer weather. Speaking for myself, working on the fuel system in this weather is a NON-STARTER. My "motivational relay" does not function below 45 degrees.

 

[DavidC]

Definitely should have a spare relay on hand for that. I always carried one in my glove box just in case.

A spare pump is good to have also. I have 2 or 3, haven't needed yet except for troubleshooting. Hopefully this goes better than the last airdog thread when I told him to get a new pump and it took at least 3 weeks for it to sink in. To the OP it is usually a 20 amp fuse from what I have seen.

 

[DavidC]

Typical remote pump

 

[JR]

Chief brings up a possibility that the filters froze. If you do find a blown fuse it is a good idea to pull the filters and check to see if you have fuel there. It would have to be dang cold for the whole rig to freeze solid - generally the fuel will gel in the filters but still be able to push back through the overflow as that does not pass through the filters.

 

[Chief USA]

Chief brings up a possibility that the filters froze. If you do find a blown fuse it is a good idea to pull the filters and check to see if you have fuel there. It would have to be dang cold for the whole rig to freeze solid - generally the fuel will gel in the filters but still be able to push back through the overflow as that does not pass through the filters.

I guess I could have been more clear. How many of us drain the water separating filter at each fill up??? I suspect VERY few of us. I'm guilty as charged. Water will settle out of the fuel inside the filter and easily freeze. Can make for a bad day if you need your truck right away.

 

[JR]

Agreed, but the filters are the first place fuel will gel regardless of whether there is water present in the fuel or not. If the fuel actually gels in the pump, fuel lines, etc. you have gotten a bad batch of fuel that was not additized for your environment.

 

[DavidC]

If the fuel gelled in the pump it probably blew the fuse due to locked rotor amps.

 

[DavidC]

Here's a question none us have asked.
Who installed the pump and remote electrical ?. Hopefully they wired as diagram and not to the original wires. Check power at the pump ?

 

[jeepit]

Here's a question none us have asked.
Who installed the pump and remote electrical ?. Hopefully they wired as diagram and not to the original wires. Check power at the pump ?

I had a friend install pump. He owns his shop and is meticulous about his work.

 

[DavidC]

I had a friend install pump. He owns his shop and is meticulous about his work.

Can you contact him and find out where he installed fuse and relay ?

 

[jeepit]

Absolutely. Once it warms up here I will look for fuse and relay....if I can't locate I'll give him a call.

 

[DavidC]

Be aware you may need a new pump. Not to shake you up but we just went through this a while ago. Just keep it in mind so it doesn't come as a shock and you can check on the warranty if any. On the bright side maybe just caused by the cold and blew the fuse.