Archived low boost

[dcamilleri]

Looking for a little help with a low boost problem on a 2001 24v (30K)that is installed in a 1985 Sububan. It has a hx35 turbo, diablo power puck, boost fooler, boost elbow, and 275 hp injectors. Fuel filter is new withing 500 miles, has a carter pusher pump back by the tank. Fuel pressure never goes below 15 psi.



I used to be able to get about 28 lbs of boost until I failed my pusher pump several weeks ago. I replaced the pump and now my boost won't exceed 20 psi. I just cleaned the MAP and IAT sensors thinking that warm up time with the Jake brake on might have the sensors dirty, no change in boost. My EGTS are a little on the low side, 1100f, wot @100mph in 5th. (ambient temp is about 15 degrees, northern Wyoming) Power feels not quite as strong as it used to ,but not at all doggy. I have checked all the intercooler boots and cycled the waste-gate(it is operating). I am wondering if the wastegate is not making a good seal and leaking some exhaust gas. Over the past week I have seen times when I could not get over 12 lbs of boost and other times when I was able to get 22lbs. No rhyme or reason. Any thoughts would be appreciated.

 

[dcamilleri]

Just for the heck of it I put in a new fuel filter tonight. Took it out for a test drive and it would only pull 16lbs of boost. Turned around and drove back and it would only pull 12lbs, but power seemed near normal. (I can't check codes without a Cummins insight tool since I don't have a PCM or Dodge ALDL port. ) I have tried disconnecting the wastegate with no difference in boost.

 

[Sticks]

I would start looking for a leak in your boost gauge assembly.

 

[akline]

I would think the EGT's would go alot higher (I'm guessing your probe is on the engine side of the turbo) with the boost that low, or you would notice a significant decrease in power. Sticks may be on the right track, maybe your guage decided to start reading low somehow. Do you have a tire guage with 1/8" pipe thread you can temporarily replace it with?

 

[britannic]

You mentioned 15psi for fuel pressure, was it the same after replacing the pusher pump? Is there any possibility of debris in the lines to the filter, or did the pump just fail electrically?

 

[dcamilleri]

Thanks Sticks

I am going to make a pressure tester today and look for leaks from A to Z

 

[dcamilleri]

I am also going to check the integrity of the boost gauge. I disassembled my old pusher pump (carter) and the rotor assembly looked good. I think the electric motor got weak from trying to push cold thick diesel fuel. Also as a note, when I used to be service manager at a tractor dealership I saw lots of electric fuel pump failures, usually right after filter replacements. Guess what brand of fuel pump? You are correct-CARTER!

 

[dcamilleri]

IT IS FIXED

Thanks to whoever it was that posted the pictures of the intake pressure tester. I built mine today and it worked awesome. And yes I found some major air leaks. I used a 4"x2" rubber plumbing reducer, inserted a pvc 2" x 3/4 pipe bushing and coupled it up to a tee with a gauge on top and an adjustable regulator on the inlet. On my first try I couldn't even build any pressure since it was leaking so bad at the elbow from the compressor housing. I disassembled it and inspected the o-ring, not great but still usable, added a little ultra black rtv and snugged it back up. Then found a clamp a little loose and leaking on the intercooler inlet. Next I found that my boost pressure feed line was split. Since it is sunday I just plugged the intake for now until I can get a new boost tube. Oo. Oo. Oo.

 

[Sticks]

Oo. Oo.



Great to hear that we could help out!