Engine/Transmission (1998.5 - 2002) Odd lift pump problem

[Mr. C]

Today I was on the way to town and noticed the fuel presure was at 3 lbs, I thought WTF! Anyhow I watched it for a couple minutes and it jumped back up to 12 lbs for a few minutes then back down to 3 lbs where it stayed. When I restarted it it went right to 12 lbs for a few miles then dropped to 3 lbs again, I slipped the transmission into neutral and shut the engine off and restarted it and it was back up to 12 lbs. Each time the presure would drop it would go back to normal if I slipped the transmission into nuetral and did a quick shutdown and restart. I put an amp meter on it at home and it read 2. 8 amps while at 3 lbs and 3. 2 amps at 12 lbs.

This is a weird way for a pump to act if it's doing the death march, anyone else have this problem? I have a new lift pump on the shelf waiting for its turn under the hood and I will change it out when it cools down a bit but I wondered if there was anything else to look at first. Any ideas?



Regards, Mike

 

[DMcPherson]

I dont think it was an issue on chrysler software but there is a campaign on isb's for losing voltage to the pump. actually Im pretty sure it does not apply to dodge. Mine did something similar as well. when yo urestart it should run its prime cycle and show yo uthe pressure you see then die off when tunning mormal cycle.

 

[darkhorse]

My '01. 5 ETH occasionally did things like that.

 

[fmj]

Mike, before you change out the transfer pump, you might want to verify that its not your sending unit. I have an electrical fuel pressure gage and it gave me a reading that showed the tp was acting up, dropping in pressure and then returning. I changed out the transfer pump only to find out that it was the sending unit. I now carry a mechanical gage that I can check the pressure at the schrader (spelling?) for both pre and post filter. Just way to double check. Sending units are cheaper than transfer pumps.

 

[RClark]

Mine does something similar. 13-14. 5 at idle. 12-13 wile running but droping to 8 at times. Havent checked voltage at pump because i havent figured out how. It seems to be almost as if whatever controls the pump voltage is dropping it to the starting voltage while running. Pump has only 10k on it and i backes up the sender with a mechanical gage just before it -they both read within 1/2 psi of each other.

What controls the voltage to the FP?

 

[Joe Mc]

This is a weird way for a pump to act if it's doing the death march, anyone else have this problem?

Mike, after the first time I replaced an LP - under warranty @ 97k (I purchased with 75k), I installed a gauge, then after replacing 3 more on my own dime (present miles @ 148k) - I must tell you that each time my LPs started to crap out they did the same thing you describe. Don't be a nim no like I was and spend however much a stock LP costs times 4 untill you do the right thing. Click HERE! Your truck and pocket book will like you for doing so:-laf

 

[DirtyDodge]

Mine did that to me a couple times before I went to the FASS. I was driving through oregon and pressure was at 12psi. Instantly it dropped to 6psi with no change in driving condtion. Then it would all of a sudden go back to 12psi. It did this to me a couple times, never knew exactly what was causing it. I went to a fass that fall, stock lift pump was not happy it's first year in a Washington winter. Anyway, hope you figure out what it is.



Derek

 

[Moose Truck]

Me too!

Mr. C, Must be weird post IRP Vibes, as my truck is doing the same thing! Lookin into an aftermarket pump now, as I've changed 3 Carter style pumps the past 2 years. Moose00