Diesel 98.5 lift pump fuel pressure ???

[rwilber]

replaced the fuel filter and found a dead lift pump...purchased a replacement carter lift pump...new lift pump is pumping. filled the fuel filter and started the truck....truck runs fine except between 50-60 mph at low rpm especially on an incline....automatic transmission,,,use 2% biodiesel

abt a 100 rpm drop, hesitation and continues to cycle through this until I put the pedal to the metal...ever so slightly

any ideas

[rwilber]

the cummings fuel filter that I removed looked different than the el cheapo I repalced it with...a $30 difference...the filtration is also different 2 micron instead of 7 microns for the cheapee. went and got another one @ dodge this morning 04883963AC. the slits in the top of the mopar filter are at least 5 times as big as the cheepee...

wonder if thats straving the vp44 at low rpm in overdrive?

[rwilber]

Soo, I'm a little confused...the lift pimp runs for 2 seconds or 27 seconds and then it turns off??? the vp44 can suck all the fuel it needs once a vacumn in the fuel line is established...if the fuel line has an air leak the vp44 sucks the air too..is that it?

[rhandwor]

I can't follow you completely but a leak in the fuel line will cause you problems. Napa filters should work fine be careful to buy a quality filter. On my diesel tractor the dyed fuel shows up very quickly if their is a leak. At over $4.00 a gallon it pays to fix leaks.

[rwilber]

installed the mopar fuel filter instead of the autozone...seems to be working much better...the gaskets and o ring differ as well as the overall appearance as noted before...only time will tellopcorn: opcorn:

[rwilber]

its still hunting for the right gear...seemed to run better until I removed the foam from the bottom of the air filter and reinstalled it foamless...I don't know anymore...gotta drive 5000 miles in a couple weeks

thinking its bad fuel

[rhandwor]

Did all this start before or after you replaced the pump. Is their a filter before the pump was this changed? Everything went together properly on the pump. All connections tight and no extra filters you could have missed. Mercedes had a couple of filters in the fuel line.
Put some in a glass jar and let it sit overnight.

[rwilber]

Thats a good idea...run it down the street and shake it up and drain the fuel filter into a glass jar and wait for any kinda separation...could be the fuel

It started after I replaced the fuel filter and then had to replace the fuel pump which sits next to the filter...used new cummings seal washers...

the other thing i did was to disconnect the batteries for abt a week and now the engine and the inj pump and transmission are in learning mode????

[rwilber]

added some cetane boost/ inj cleaner and it started to run better immediately...

on a side note,...my '99 grand marquis was miss firing right and left
on a tank of 87 octane/ethanol... I suppose they mix 90% 87 octane &
10% ethanol which probably equates to abt 85 octane mix...bought some chevon additive and the problem stopped immediately

on another side note,...any amount of ethanol voids the warranty on my cadillac

[rhandwor]

I'm glad you fixed the problem. I put a bottle of Gumout diesel injector cleaner in my tractor fuel tank every winter. It helps prevent problems. You have to be aware where you buy fuel for your Cadillac.

[rwilber]

Fixed the problem finally...the problem was in the torgue converter clutch;
unlocking and locking when it should be locked..rpms ( 50 to 100 ) would decrease and then increase continuously especially on inclines above 45mph . Dodge TSB 18-02-99 talks about this somewhat. The problem was the ground from the PCM to the battery. Follow the negative wire from the passengerside battery past the air filter to the PCM mounted on the fire wall.

Clean the grounds on both batteries, clean the termainals on the batteries, disconnect and reconnect the quick connects and disconnect and reconnect the three 18 prong connectors on the PCM. Clean the grounds from the battery to the truck body. Clean the ground from the battery to the PCM.
Reconnect both positive terminals and then reconnect the negative battery terminal driverside and then the negative terminal passengerside.

turn the iginion key to on, don't crank, depress the gas petal and slowly release it. remove the key from the iginition.

I also distanced the negative ground to the alternator from the other wires to the alternator with my fingers.

[crash_1333]

i am not to sure about diesels but if it has injectors maybe one or acouple are alittle cloged....let me no if this helps