I may have a problem with my lp or fpg not sure.

Yesterday I started my Cummins and noticed that the dash buzzer and wait to start light did not come on. The truck had been sitting for eight days without starting. After starting I noticed the fp fluctuated between 28 and 20 several times while at idle. Once driving it fluctuated between 18 and 24.

 

The only thing I have done was changed the fuel filter when I serviced the truck about fifty miles ago. I installed a Donaldson ff. I believe I read that the Donaldson ff was 10 micro. I cant figure this deal out. Anyone had this problem before?

First thing to do is verify fuel pressure. Is your gauge electric?

I've seen my  fp   up and  down  during the   grid  cycle (after cycling)..    it'll do it     5-6 times.   My  dash voltage  drops  to   9-10 volts  when  grids  kick in,  that'll sure  drop  fp!

I  wonder  why  yours   'skipped'  the  preheat.  Was  this  a  'one time occurance'    Did the  FP  bounce after    the engine  was warmed up  ( or on a  warm  restart?)

 

How cold  has it  been  while the  truck's  been sitting?   where  is  your  pressure tap  at?  

Edited March 2, 201411 yr by rancherman

Check your grid heater relays.

First thing to do is verify fuel pressure. Is your gauge electric?

 

I tend to agree double check your fuel pressure with a mechanical gauge. Electric gauges are know to die of water hammer pulses beating the sender to death. Most people don't protect their gauges so the elctric gauges will fail without warning to the driver. What's really bad is the gauge typically fails to higher pressure not to ZERO like you figure it would. So most people drive blindly thinking they have fuel pressure but the gauge is wrong.

Mopartechnician, Autometer electric

 

Rancherman, One time occurance, normal pressure is 24 idle, 18-20 crusing, 16-18 wot. Pressure tap is a Hydrolic Needle Valve plumed

 into the fuel filter on the vp44 side.

 

Molon Labe, will do.

 

Mopar 1973 Man, I have a needle valve installed between the factory fuel filter and the guage

 

We have had a week of cold weather, -20* at nite. I will check everything and post it. Thank's friend's.

Mopar 1973 Man, I have a needle valve installed between the factory fuel filter and the guage

 

 

Does you gauge rise slowly to position or snap to pressure?

One timer eh?     are you talking about the  lack of  pre-heat,  or   the   pressure  variation?

-20 F  is pretty cold,  you might've  had  some  gel   issues too.      Welcome to the  club!  

This happen  immediately after  you changed  the filter,  or  after the  cold snap  it  sat through?     after that cold snap,  there may be  some  nasties  in your tank..  (spring  is  around the corner!!).   

 

Just for giggles,   open up your needle valve,  just for  checking purposes.   After  you  see if there is  any change  in the  gauge,  put it back to where it was.    A short time  un dampened  shouldn't  hurt.  ( I mean SHORT)    I've  seen  needle valves  change  big time  just  with a  swing in  ambient  temps,   vibration  can   screw them  in or out too..  Yours may have  a  blob, or  closed too much. 

How many miles you have on the  lift pump now?

 

 

 

I don't know  what  the  threshold is  for  'pre heat,  or  no  preheat'  or  what  is  used  to  decide.   IAT?    I've  read on other forums  about  the odd occasional   'lack'  of  preheat.  possible   pre start  circuit  didn't boot up?

Mopartechnician, Autometer electric

 

normal pressure is 24 idle, 18-20 crusing, 16-18 wot.

 

 

I would guess you have a bad gauge. And you should never have fuel pressure above 20psi, you are just asking for trouble.

 

I don't know  what  the  threshold is  for  'pre heat,  or  no  preheat'  or  what  is  used  to  decide.   IAT?    I've  read on other forums  about  the odd occasional   'lack'  of  preheat.  possible   pre start  circuit  didn't boot up?

 

Anytime the IAT sees that the temp. is 65 or below. After running the truck around a little or longer, the truck is warmed up and the temp. will obviously be above 65 at the IAT sender. Therefore, the grids do not cycle like you would expect when the truck is cold because it measures the intake temp. Not the ambient temp.

Anytime the IAT sees that the temp. is 65 or below. After running the truck around a little or longer, the truck is warmed up and the temp. will obviously be above 65 at the IAT sender. Therefore, the grids do not cycle like you would expect when the truck is cold because it measures the intake temp. Not the ambient temp.

Okay, The weather here was from 23*- 32* for about ten days when I made my post. After reading all suggestions I started thinking and decided since I did not need the truck for the next week I would just let it sit till the weather warmed up. Today is the third day of sunny warm wearher, about 72* so I drained my diesel/water separator and started her up. She started on the first hit and the FP guage read as It should. I want to thank all you guys for sharing your thoughts with me.