Air Dog Overheating

[Ataylor]

Hi everyone,

I finally got my truck running and timed. Many thanks to all that have responded to my questions during this overhaul. I'm very greatful to have found such a great source of info on these trucks.

I'm currently having a problem with the Airdog fuel pump/filter getting very hot while running. It has only about 2 hours of run time. I have replaced everything on the fuel system. New in bed fuel tank with 30 galllons of fresh fuel and additive(old tanks removed), large prefilter before the airdog, all new fuel lines to and from the engine and tank, new Baby Moose IP, new BB injectors, new return caps and lines.

I noticed tonight that when I went to start the truck that I didn't remember hearing the Airdog start pumping like normal before I cranked the engine. Truck started without needing to glow the plugs and I ran it for about 10 minutes. While running I went under the truck and felt the pump to see if I could feel it running and it was really hot and did not seem to be spinning. It was hard to tell with the engine running and I know these engines will run without the lift pump functioning properly.

I shut the truck off, and turned the ignition to the run positition and I heard the pump start and run. I could hear it recycling fuel back into the tank, but again when I went under the truck the pump was very hot to the touch. The relay for the pump which is in the engine compartment was also warm to the touch. I used the complete wiring harness and relay that came with the Airdog kit and it is wired directly to the battery per their instructions. When checking for power to the Airdog it has full battery voltage.

When I first tried to fire the engine the first time since the fuel system overhaul, the Airdog wouldn't spin. I called Airdog and they said to remove the pump take it apart and check that the rotor was free to spin with the cover removed. They said that because the pump had sat so long that the prelube could have gummed it up. I took it apart and it was free to spin. Reassembled with a little white grease per their instructions. It has been working everytime I turn the key to run, but now it is getting hot. To be honest, I have not felt the pump before tonight, so maybe it was running hot this whole time, but I didn't suspect anything was wrong because I could hear it pumping fuel whenever I turned the key.

So my question is, does anyone think that the pump is getting hot because it is having to suck through the prefilter? Too much restriction?

The prefilter is a large Napa filter head and large filter with -8 AN lines running from the tank to the prefilter and to the Airdog. The Airdog has it's own water separator and filter, but I thought the prefilter was a good idea. The fuel line from the tank including the prefilter is only about 4 feet before the Airdog and it siphon fed itself so I didn't even need to fill the filters to prime before I started the truck for the first time.

I would hate to have to make new AN fuel lines to take the prefilter out of the loop. And I'm not looking forward to removing the Airdog to take it apart again now that it is full of fuel, but it looks like thats what I'm going to have to do. I have a Airdog on another truck and it has been very reliable, but it doesn't have a prefilter either.

Thanks for any advice anyone can offer.

Sorry for the crappy pictures, it was dark.

Archie

 

[sle2115]

Looks like it would be easy to plumb around that pre-filter for a trial, short piece of tubing with pipe fitting on each end. If it were me, I'd try that and see what happened, then go from there.

I run a pre-filter on my Carter, but it doesn't have a filter on it either. Are you still running the IH filter head as well? If so, I'd say you may have a little to much restriction and the pump is working hard, that and you may not have enough fuel flow to cool the pump. When you contacted them (Air Dog) did they say heating of the pump was normal?

 

[Darrin Tosh]

Is this an Air Dog II with the adjustable regulator? What PSI is it putting out? These IDI's only need about 10 PSI to push the pumps, and these Air Dogs put out way more than that.

 

[Ataylor]

SLE2115, Good idea- I will try to plumb around it and see if that makes a difference.

Darrin Tosh,
It is a Airdog 100 kit (non adjustable) normally used on the GM 6.5. The regulator spring on these is set for 8 psi of pressure. When I sent my IP to Mel to be rebuilt I asked if the inlet pressure could be set a little bit higher. I have a Autometer fuel pressure gauge that is wired up, but installed yet. So I'm not really sure what kind of lift pressure the IP is seeing from the Airdog. If it still too high, Airdog said that I could tweek the regulator spring a little bit to lower the pressure if needed.

Thanks for the info,
Archie

 

[SparkandFire]

Most pumps like this (submerged impeller) require a certain amount of fuel flow (i.e. volume) in order to cool the motor.

Perhaps it's rated at a higher volume of flow than you can obtain with your stock system. Look at the bleed line on top of the fuel filter housing, the hole in that fitting is tiny, plus the bleed line on top of the IP is tiny.

I think you might not be flowing enough volume to cool the pump adequately.

 

[RLDSL]

Take that airdog off and throw it away. You have ZERO need of that thing IT was designed for electronic injected diesels that fire multiple times per stroke that would cavitate on the air in teh fuel and only fire maybe 3 out of 5 times that they were intended to, but with our mechanical injection systems , we have zero need of teh things, and the volume of fuel being moved by that thing is far more than your return system is setup to handle which is why it is heating up. Get rid of it, get one of the e pumps that has been proven to work on these things without a problem like a Facet Dura lift and you will be in business.
THings that work great on Duramaxes and Cummins and powerchokes are generally useless on these engines.