Fuel pump "fix"

[RawbDidIt]

My truck has been on the weak side lately, especially prior to being warmed up, so I decided to do a little diagnosis of the problem. I'm posting this as a help for others who may experience the same issues.

Symptoms: sluggish acceleration especially from a dead stop, uphill, or prior to reaching running temperature. "Lurchy" acceleration from a dead stop, or uphill.

I cleaned the throttle body with no difference, and then decided to check the fuel system. When I got the truck the fuel filter was so clogged the fuel coming out was brown, like half used motor oil. Since I've changed the filter already I figured it's probably the fuel pump. Not surprising given the state of the filter before I replaced it. I'm doing an engine swap in a few months at my dad's shop so I'd like to swap the fuel pump then when I have the tools to make it much easier so I thought I'd try to make the one I've got work better.

Now my dad's a bit old school, and suggested something a bit odd, but he's one of those guys who is rarely wrong and I figured the worst it would do is push up my schedule on replacing the pump. He suggested I put a quart of transmission fluid in the gas tank, says it lubricates the pump and should get it running better. Sure enough, it worked. Only problem is it didn't fix the lurching issue, and after driving for 30 miles it did throw a code. P1405 turns out I have a bad EGR valve. I have no idea if the ATF burns a bit dirty and finished off the EGR valve, but my guess is it was already on its way out and just didn't throw the code yet. In any event, just thought I'd share this in case anybody was having a similar issue.

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[454cid]

Explain how it "worked" if the problem didn't go away, and now you've got a code?

 

[RawbDidIt]

Had 2 problems, the throttle response is better, but didn't fix the lunging from a dead stop.

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[454cid]

You need to get a fuel pressure gauge on it.

 

[RawbDidIt]

Probably should have put this in the original, but the code for the EGR valve wasn't new, I pulled the EGR valve and the inside had way more carbon buildup than could have been made by just adding a little bit of ATF to a full tank of fuel. Throttle body cleaner didn't clean it enough for it to operate correctly. I was already ordering a new one, but a bad EGR valve doesn't get better after the engine warms up, so I knew there was a second problem to diagnose.

Yes, I could put a gauge on it, but it isn't going to tell me anything I don't already know. The engine wasn't getting enough fuel, now it is. One problem solved, and I ended up finding the source of the other problem. I'm calling it a win.

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[Supercharged111]

The ATF will clean everything it touches as it passes through the sytem. It's just not all that good for O2 sensors and cats.

 

[RawbDidIt]

The ATF will clean everything it touches as it passes through the sytem. It's just not all that good for O2 sensors and cats.

Thanks, I'll keep that in mind. I'm sure the o2 sensors are on their way out. The previous owner didn't take the best care of the vehicle. Might delete the cat anyway since I'll never have to smog test her.

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[Ken K]

Did you ask why your fuel was brown when you dumped out the fuel filter? Changing hundreds of fuel filters at the dealer (rusted housing), I always tested how plugged they where over the solvent tank. The brown stuff is small micron sized dirt & dust. It comes from gas stations and over the years, builds up in the tank. While many pull the bed to service the pump, they find the pump fails in a few months. The tank has to be removed, drained properly, wash with the hottest water you can get in it, rock it back & forth vigorously then empty. Clean by hand as best you can, perhaps will paper towels and place in a warm spot in the garage to dry. Sound crazy? GM places this procedure in there fuel pump replacement procedure if after inspection you find the sock brown or contaminated. Modular fuel pump assemblies have the plastic bucket. There is a filter on the bottom and another inside on the pump body. Three tabs will allow the bucket to be dropped down for inspection. The filters are progressively finer and the fine dust / dirt settles in there. Carb guys...ever remove the paper filter, cut it open, turn it up-side down on a white paper towel? After it dries, tap on it and watch the dust fall out. This destroys electric fuel pumps. The ATF in the tank is a nice touch, but today fuel pump armatures are designed with "Low Lubricity" and use different brushes and commutator plates. Fuel pumps are not garbage disposals...just inspect and choose they proper procedure.