Engine/Transmission (1998.5 - 2002) LP stops running

[DonS]

Turn key to "on", I get the short (1/4 sec?) burst on the lift pump. Start engine, I have ~18 psi. After idling for a minute, or so, the lift pump shuts off. Turn engine off, wait 30 seconds, and lift pump is "working" again - for another minute.



I don't think I've seen this as a symptom of a dead LP. I do have a brand new one sitting on a shelf, and it's easy to replace, but I thought I'd first ask if anybody has had a similar problem, and if replacing the LP fixed it.



I can also reproduce the non-running-LP symptom by cycling the key from off to on and back a few times. The first couple of times, I'll get the short burst. After that, it's dead until I let it "rest" for 30 seconds or so.



EDIT: One thing I have noticed... for the last couple of days, my idling FP has been about 18 psi. It used to be about 14. This change seems to correspond with the installation of the Comp. Could the added fueling demands of the Comp have killed the [original] LP?

 

[DonS]

I decided to go ahead and swap pumps - just because it's so easy with the relocated setup.



That seems to have fixed it. I cannot reproduce the problem, and I'm back to my expected 14-15 psi at idle, 12 psi in crop dusting mode.



Time to throw one pump in the trash, and order a new spare.

 

[VIPERBLUELX]

Is the rest of your fuel system stock or do you have the larger lines and relocated pump?

 

[DonS]

Is the rest of your fuel system stock or do you have the larger lines and relocated pump?

The "Vulcan kit" in my sig is referring to the full, 1/2" relocating kit direct from Vulcan. That is, I have 1/2" blue garden hose from the LP to the IP, 4" of 3/8" between the tank and the LP, no banjo bolts, and the OEM Carter pump is on the frame rail just in front of the tank.

 

[VIPERBLUELX]

This question is unrelated to your issue, but after installing the Vulcan kit did it help your fuel pressure at WOT? I have a brand new Carter pump but the rest of the fuel system is stock. I have 12psi at idle, 8-9 cruising, and it drops to 4-5psi at WOT if I hold it WOT through 2 gears or more. I'm hoping the Vulcan kit will help.

 

[DonS]

This question is unrelated to your issue, but after installing the Vulcan kit did it help your fuel pressure at WOT?

Yes, it did help. Before I ordered the Vulcan kit, my only fuel-related mods were the Smarty and the injectors. At idle I had about 12 psi, but it would drop to about 6 psi at WOT. After installing the Vulcan kit, idle was about 15 psi, WOT was 11-12 psi.



My FP did flutuate a bit after installing the Vulcan kit. At first, the pressures didn't change from pre-Vulcan. One morning, though, they jumped to the 15/12 levels I later considered "normal". I think my LP may have been flakey already.

I have a brand new Carter pump but the rest of the fuel system is stock. I have 12psi at idle, 8-9 cruising, and it drops to 4-5psi at WOT if I hold it WOT through 2 gears or more. I'm hoping the Vulcan kit will help.

Based on your mods (specifically, the lack of current fueling demands), I'm not sure the kit will help. However, your situation is the the reverse of mine: I added fuel demand first, then moved the pump. I didn't even have gauges until after the Smarty, so it's possible (likely?) that my pressures, at the stock configuration, were like yours.



EDIT: after re-reading my post, I'm not sure the Vulcan kit did help at the time I installed it. My LP may have already been on its way out, and that could've contributed to the bad pressures I saw. However, there's no way I'd run my current configuration (Mach 4s and Comp) without "big" lines.

 

[DonS]

To clarify, here is the sequence in which I did the mods, along with the fuel pressures I saw:

1. Smarty

2. Gauges

3. FP was 12 psi at idle, 8 psi at cruise, 4 psi at WOT

4. Installed injectors - FP didn't change

5. Installed Vulcan kit - for a few days, FP didn't change

6. One morning, as if by magic, my FP changed to 14 psi at idle, 13 at cruise, 11 at WOT

7. Installed Comp - immediately, FP went to 18 psi at idle, 15 at cruise, 10 at WOT

8. This morning, LP stopped running

9. Replaced LP - FP now 15 at idle, 14 at cruise, 12 at WOT

 

[VIPERBLUELX]

Yes, it did help. Before I ordered the Vulcan kit, my only fuel-related mods were the Smarty and the injectors. At idle I had about 12 psi, but it would drop to about 6 psi at WOT. After installing the Vulcan kit, idle was about 15 psi, WOT was 11-12 psi.



My FP did flutuate a bit after installing the Vulcan kit. At first, the pressures didn't change from pre-Vulcan. One morning, though, they jumped to the 15/12 levels I later considered "normal". I think my LP may have been flakey already.





Based on your mods (specifically, the lack of current fueling demands), I'm not sure the kit will help. However, your situation is the the reverse of mine: I added fuel demand first, then moved the pump. I didn't even have gauges until after the Smarty, so it's possible (likely?) that my pressures, at the stock configuration, were like yours.



EDIT: after re-reading my post, I'm not sure the Vulcan kit did help at the time I installed it. My LP may have already been on its way out, and that could've contributed to the bad pressures I saw. However, there's no way I'd run my current configuration (Mach 4s and Comp) without "big" lines.

I do already have the Powermax installed, although it's a small box, i'm sure it's hurting pressure some.

 

[DonS]

I do already have the Powermax installed, although it's a small box, i'm sure it's hurting pressure some.

Ah - ok. (you need to update your sig )



The Vulcan kit sure can't hurt and, whether you replace the OEM pump with something else or not, the larger lines / no banjo bolts are a pretty good idea with any kind of fueling mods. One of the last things you want to do is starve your VP44.