Archived crazy FP readings

[dieseldawg]

:{ Installed fuel pressure gauge @ 199,600 :{ :{ :{ pressure @startup 12 romp through gears and @ each shift drop in pressure to zero then back to above 15 WHAT THE also any severe punch on the accelerator pressure drop to zero then back to above 15. Tried the same scenerio without the drag technique only difference was after a drop to zero pressure returned to 12

 

[WadePatton]

Time for a new LP.

 

[dieseldawg]

SORRY MILEAGE @ 99,600,brain frazzeled too many decisions. Stock LP or ADT PE 4200 . Warranty or ?$$ for ADT also with ADT return my 245$ 0-15psi FP gauge for 0-40 gauge. I wonder how AutoMeter works with returns. DECISION ... . RELIABILITY

 

[WadePatton]

Some Bosch guy said that your VP-44 should NOT see more than 12 (or 15- I forget) PSI at the inlet.



What in Heck would you be doing with a 40 PSI gauge?



I don't know what else you are talking about.



My first LP was fine as long as no WOT + load. Then it would sink to 2# or less--immediately recovering. I replaced it. Never less than 6# now and that's at 40# boost.

 

[B.G. Smith]

Lift pump

The lift pump is covered by the engine 100,000 warranty. From my experience, unless you have a dealer who is very knowlegable about the Cummins I doubt that you can get them to do anything as long as the truck will run. If you have to put out the $$ I would go with the aftermaarket pump. bg

 

[rblomquist]

Don't know if it matters but I just had my LP replaced under warranty this week. My dealer told me that the LP is covered under the 8/80 specific emissions warranty (not the 5/100 engine warranty). Also, my pump was showing decent pressure 6-7lbs UNLESS I was under load (then down to 3)

 

[Pit Bull]

Lets talk pressure versus flow I submit that if you have any pressure you have positive flow and your VP44 is getting all of the fuel it needs. :-{} :-laf :-laf

 

[dieseldawg]

PB ,

so hence when I have 0 pressure I have 0 flow

 

[illflem]

Not really, you can have flow with no pressure or even vacuum.

 

[TowPro]

98 is the same way, 8/80 HD emissions warranty. I think in 2000 they relized this was taking out the big pump, so they upped the warrantee to 100K.

Originally posted by rblomquist

Don't know if it matters but I just had my LP replaced under warranty this week. My dealer told me that the LP is covered under the 8/80 specific emissions warranty (not the 5/100 engine warranty). Also, my pump was showing decent pressure 6-7lbs UNLESS I was under load (then down to 3)

 

[Pit Bull]

Originally posted by illflem

Not really, you can have flow with no pressure or even vacuum.

I agree, when my LP died and I measured FP pressure I measured a vacuum Not what I wanted, but the truck ran fine, no noticeable performance change. But I got it replaced. Now I check it every month So far so good.

 

[Bigsaint]

As always, Mr. Bill is right on regarding flow. When my first Mallory died, I was seeing a vacuum reading of -11 on the SPA FP gauge . Unfortunately, that flow is from the VP44 sucking the fuel, hence the vacuum. Mine would idle fine, but ran like crap when I tried to limp it home. I stopped and had it flatbeded and that is another story in and of itself.





DD... don't fool around and burn your injection pump out. If DC will not help ya just do it yourself, pronto IMHO.



Scott W.

 

[B.G. Smith]

And

You could have vacuum, pressure and a little flow. If the fuel filter is plugged and you are reading the pressure after the filter, you need to change the filter before you condem the pump. When mine went out I took it in and the dealer kept it 4 days, got it running somehow and I brought it home, checked the pressure and it was negative reading even at idle, called another dealer and he picked it up and replaced the pump the same day. bg

 

[dieseldawg]

OK, GET READY EVERYONE!!!!!!!

Went to the dealership on friday, NO pump in stock (269$),have it on monday we promise. So I went to CUMMINS WEST, 2 pumps in stock (145$)ea . Purchased the pump and also the trouble shooting and repair manual (69$). Also stopped by the local parts store and purchased a mechanical test gauge ,to test against the new autometer. Started the project after reading all the possible pressure tests points, and fuel problem scenerios. Tested all points with both gauges, same outcome! : Time to replace the pump . 20 minute job, as long as you've twisted all your banjo bolts 15 times in and out like I have searching for answers So, next round of tests, all points,with both gauges. ... ... ..... You guessed it , same outcome ... ... ... .





Last thought , could the drop in pressure I am seeing, be due to the plug N power pulling too much for the lift pump to keep up with.

 

[Snow man]

Ist thing,change the fuel filter,you didnt mention replacing in your Fuel Filter in the 1st post. Thats whats wrong with it,IMO,your old lift pump is probably fine. Ive had 3 filters do the same thing in 15K miles,change them,and the fuel pressure returns to normal under heavy load. You said your pump could hit 15psi, between shifts,then it was probably fine,sick lift pumps rarly get over 11-12 psi at idle.

 

[dieseldawg]

sorry snowman, I replaced the filter on wednesday:{ :{ :{

 

[Snow man]

dieseldawg,no problem,now what to do?Maybe a restriction in the in tank pickup sock?

 

[Bigsaint]

DD, with the gauge checking pre-filter, how low can you pull it down ? There's now way just a BD box will drop your psi's like you are seeing, IMHO.



Snow Man might be onto something, isn't there a screen of some sort in the tank ? Or possibly the inbound fuel line has a air leak ?



Scott W.

 

[dieseldawg]

Ouch! Ouch! Ouch! Ouch!

Have to take off the bed to check the sock!!!!!

 

[dieseldawg]

OK,

Today I disconected the BD box and tested the system. The same problems still exist ,only now the pressure only drops to 6.



Next I pulled fuel line at the quick connect just before the lift pump, and blew into the line. I was amazed at the restriction, definately not a free flow from the tank





I guess tomorrow means bed removal