Engine/Transmission (1998.5 - 2002) Low reading on fuel pressure-Cold start-up?

[Turbo Terry]

I recently installed a in dash fuel pressure gauge. Up until now I was using a Miller test gauge to check my pressure and doing it while engine was HOT. Now I notice when its cold out and I first start up that my fuel pressure is low until the truck warms up . Is this normal ? What readings are you other cold weather diesel owners seeing at start up.

 

[BarryG]

Mine are lower at cold start up sometimes as much as up to 3-4psi.

 

[RBallard]

I am running the Westach FP gauge. In the summer months the truck ran 13 psi idle and 10-psi cruising. With my last fuel filter change and now the cold (in-the-teens) weather I idle 10 psi and cruise 7-8 psi. I see a slight difference in pressure between Virginia fuel and Pennsylvania fuel and I just associated that with the assumption that PA thins their fuel more when winterizing it.



Bob

 

[TboneMan]

I have notice that my Westach FP guage (electric) will read low when the grid heater is cycling. If the weather has been cold you might be seeing the voltage drop caused by the grid heater.

 

[CFAR]

Yeah mine is low on start up, and the grid heaters will drop it at least 3 psi when they cycle.



Mine is 13 psi warm idle, 9-10psi cold idle (no grid heater)

on start up pressure comes up slow.



before filter change idle numbers were the same.



after filter change cruising warm = 8psi

cold = 6psi

before filter change

WOT didn't do it

3/4 throttle warm = 0psi

cold didn't do it



after filter change

can't get it much below 3psi under 85mph,

Still feel I need a lift pump, but I'm happier with these #'s

I have a hard time checking my psi #'s, clutch won't hold 3/4 throttle anymore unless I'm over 2300rpm.



Scott you out there, time for the CON-FE

 

[Diesel Gunner]

Mine is at the stealer today for low FP. On cold start up, I could only hold 5-6 lbs. while the grid heaters were cycling. At idle warm, it would only maintain 9 psi.



I had taken it in about 3 months ago and they told me that it was still holding 10. 5 psi at idle warm and they would not replace the pump until it went below 10. They also felt that my gauge was not accurate. Not even a thought that theirs was off. I am sure that Westach would agree that their product is inaccurate and not worthy of diagnosing something like fuel pressure.



Anyway, I told them that it had gone down from 13 psi at idle warm and that I would bring it back when it was below 10. I am just a dumb customer who buys junk aftermarket products so why listen to me, right?



Believe me, if it weren't under warranty, I would not have taken it back. With any luck it will be one of the "new" punps and will last longer than 38k.



Cfar, if you are still getting those FP numbers, I would get that pump changed. Good luck, gentlemen.

 

[TORQUE THIS]

I have noticed that the last few days, dosen't matter if it is at start-up or operating temp, while sitting still, pressure will go from 16 down to 6 or 7, and then back to 16. With the truck going down the road it maintains 14 to 15. Is this a sign of a bad lift pump. Can a lift pump for an 01 be purchased from Summit??

 

[Turbo Terry]

I see 13. 5 HOT idle and 8-9 psi at cold start-up temps in the teens. Once warm its normal and only goes down 2psi normal driving and 8-9 WOT. I think its just cold fuel? Runs OK When parked in heated garage it does not drop at all and starts at 13. 5 psi.

 

[illflem]

Sort of funny that my 12 valves see about 5 psi higher pressure when it's real cold. It's the opposite when it's real hot, the pressure drops. Other 12 valvers have reported the same. I always figured the viscosity of the fuel changed according to temperature causing a corresponding change in pressure.

 

[Bigsaint]

Mine is actually 1-2 psi's higher when cold ( grid heaters off) with the PE pump. When I was running the Mallory pumps my FP was always lower in the winter months, seemed to rise higher the further I drove ?? I wouldn't pay much attention to FP when the grid heaters are on as they draw mega amps. and you will see the FP gauge needle swing down when they activate.



My thinking, and I don't know if I'm right, is that cold fuel is thicker and would normally cause higher psi's.



Scott W.

 

[Dheadington]

low fuel pressure

mine did same thing when cold starting dropped to 6 psi and on acceleration dropped to 0psi. After running truck for 20-30 minutes it would go back up to 12psi and 9 on acceleration, dealer replaced pump under warranty few months ago no questions asked.

 

[Diesel Gunner]

Well, I got my rig back from the stealer last night with a new lift pump. Now at cold start I get 10. 5 psi and after everything is warmed up it will hold 13. 5 psi. At WOT it only drops to about 10 psi. And cruises at about 12.



Strangely, it seams to pull harder and accelerate faster with the peddle to the metal. I am not saying like a comp box change, just a bit smoother and stronger. Anyway I am much happier now than before.