Engine/Transmission (1998.5 - 2002) Gauges are in... LP Failure?

[Troy S]

The gauges are in. Pics can be seen here: http://smallnet.webhop.net/truck/index.htm



I need antoher opinion on my fuel pressure readings. I bumped the starter and I get 9 PSI. When starting it the FP drops below 5-7 PSI (the FSM guide), although I didn't pull the fuel system relay to the PDC to really check the cranking PSI. The truck starts very easily so it's a little hard to tell cracking PSI for sure. Fired up the engine and I only get 7 PSI at idle.



Last night while driving it I remember seeing 7-8 PSI under normal driving conditions (70 MPH with 3. 55's). Under WOT I saw VERY low FP readings, like 0-2 PSI. Under idle at times I would see 11 PSI.



At this point I'm thinking that my LP is bad? Does everyone agree?



Also, under WOT I was seeing my boost hit 22-23. I thought the max for stock is 20 or 21?

 

[01smokinram]

Lift Pump

Sounds like the lift pump has went south on you. Before you go to dealer change the filter to see it that helps out. After you get the LP replaced get some banjo bolts to help releave some of the LP from working so hard. It's covered under the 100k warranty. If you have any power boxes take them off before you go.

 

[Troy S]

How does the banjo bolt help out the LP so that it's not overworked?



No power boxes installed so I'm good there.

 

[Mtngoat]

Banjo bolts ="bigger holes" = less restriction = more fuel.



Robin

 

[kaptn]

My fuel pressure never drops below 8 psi, never. I have almost 50,000 miles on mine I might have to bronze it and put it on the mantle. good luck

 

[Troy S]

The truck's in the shop and we'll see what dealer has to say.



While driving it to the shop yesterday I was able to get the following numbers:



7 PSI cold at idle.

10. 5-11 PSI warm at idle.



7-8 PSI cruising.

4-5 PSI WOT.

 

[JBlock]

Who Guage kit

What manufactor and source did you get your guage kit from?

 

[RustyJC]

Originally posted by Troy S

While driving it to the shop yesterday I was able to get the following numbers:



7 PSI cold at idle.

10. 5-11 PSI warm at idle.



7-8 PSI cruising.

4-5 PSI WOT.

It sounds like you're reading post-filter fuel pressure. When did you last change your fuel filter? With my dual fuel pressure gauge, I can see 16 PSIG pre-filter and 11-12 PSIG post-filter on a cold start (with a fresh filter), but both are reading 16 PSIG within 30-60 seconds.



Rusty

 

[Jamie Attridge]

Let us know where you are testing the fuel pressure it makes a big difference in the readings

 

[Troy S]

Westach gauges bought through Genos. Taking readings at the schrader valve; connection shown in the picture at the URL listed earlier in this post using the 18" fuel pressure line supplied by Genos (LAHF-FL18).



Fuel filter was last changed with a Fleetguard less than 500 miles ago.



I must be missing something with the fuel sending unit hookup...

Where is the connection made for pre-filter readings?



Dealer called back and said everything is fine.

 

[Billy Diesel]

Those numbers are exactly the same as mine is posting after installing the gauges this weekend. I went with the tapped banjo bolt instead of the schrader valve. The 4-5psi at WOT has me worried. I am getting a new filter, and then I will see how it does. 30K miles so far, and 1,000 on the filter.

 

[jmtandem]

lift pump in, low pressure

The exact thing happened to me with 36,000 miles on it. I installed the guage and could not get more than 8-9 psi at idle. At first I thought it was the gauge, my installation, or something else. Dealer installed a new lift pump under warranty and with no hassle. Supposedly, the guage should be over 10 psi at idle. I now have 14+.

 

[Troy S]

here's where I hooked up the fuel pressure gauge:

#ad

 

[jmtandem]

fuel pressure gauge sending unit location

Troy,



There is about 1-1. 5 psi loss across (through) the fuel filter. I hooked my gauge sending unit up to the test port pre filter that is located on the firewall side of the filter housing (facing the firewall or facing the driver). I understand that is where Dodge tests for 10 psi or better at idle. When you go to the dealer (if you do) you might let them know you are not getting the numbers you think you should be getting from the gauge but you might also have them check something else, like listen to the idle or anything else. That was advice given me before I trotted to the dealer with a fuel pressure gauge that had low numbers but a truck that ran just right. I asked them to check the fuel pressures and to listen to the idle. Their conclusion was the lift pump was bad and covered under warranty.

 

[Troy S]

Sounds like I may be hooked up post-filter then since you say the hookup is on the firewall side of the filter canister. I'm hooked up on the fore side of the canister rather than aft.



The dealer said they found no problems when they tested it.



On the way home yesterday I was once again seeing below par pressures until about 20 minutes into the drive. Then my idle went from 7-8 PSI back up to 10. 5-11 PSI.



I had a friend of mine that performs professional jeep and truck work hook up the gauges and I wasn't there to see what he did...



Is it also a possibility that the added fuel hose and sending unit need to be bled? Is this even possible with the way the Westach sending unit hooks up?

 

[jmtandem]

fuel sending unit

Troy,



I didn't bleed the lines from the test port to the gauge. I have the same gauge. My opinion, ask the service manager at the dealer what pressures they were seeing and how they tested for those pressures.

 

[Troy S]

Go figure...



The dealership didn't actually run any tests. According to my service rep. , the tech. took the truck out for a drive and it ran fine... case closed. He proceeded to tell me that most of their techs aren't certified in diesel and that they refer their diesel customers to a cummins place in South Richmond. I asked him, "so there's no gauge to hook it up to to see, even if I were to pay for it?". Once again I got the referral to the cummins place. I won't be seeing the inside of that service department anymore.



If I take it to the cummins place and they find that the LP is bad, will it be replaced under warranty (there's another Dodge dealer a few miles away that i could take it to but I doubt their diesel knowledge is any better)? The reason that I ask is that I bought the truck used and I'm 500 miles away from 36,000. I have a long trip coming up that will put me over 36k. Also, is the 100k powertrain warranty transferrable to me?



Thanks for all of the help you all provide.

 

[Troy S]

I called the cummins place and he said they can certainly perform the test, that it's an easy gauge test (as everyone on this board has said), but I'd need to take it back to the dealer if it needed replaced under warranty. He suggested giving the service dept. heck since they never performed the test and don't know what they're talking about.

 

[jmtandem]

lift pump vs. low pressures

Troy,



Here are the issues as I have learned from many sites on this TDR. The drivability of the truck could be just fine without a working lift pump but that does not mean the pump is working just right. Apparently the much more expensive fuel injection pump is dependent to some extent on lift pump fuel flows to cool the injection pump. Excess fuel to the injection pump goes back to the tank, as it flows through the injection pump it cools it. Less pressure can equal less fuel for cooling especially at higher power settings. Without those flows the injection pump can fail. If it fails, the truck stops running. For the service manager to tell you that all 'appeared' well when in fact they did not do a test, is hardly customer service. Your gauge should have given them enough evidence to take it to Cummins to get it correctly tested. Your gauge indicatd that there certainly could be a lift pump beginning to fail and for the dealership to ignore that data is poor diagonstic service. I have much more faith in Cummins than Dodge on the engines anyway. Let them do warranty work for you if at all possible. This is just my take on what you posted, maybe it will work out for the better with Cummins looking at it and fixing it if it is bad. To the dealer's credit, they admitted that they are not into fixing or testing diesels and for you to be able to use Cummins is probably a blessing.

 

[Troy S]

I called the other Dodge dealership in the area and asked,"Do you all have the gauges needed to check lifter pump pressure on the Cummins?". The service rep. told me that they didn't and that it'd have to be done at a diesel shop. When I asked for clarification he said someplace like the Cummins shop.



Why is this so hard?



Edit: I forgot to mention that I asked the Cummins guy about the failing of the lift pump causing the injector pump failure (I've been doing my reading on this board . He said, "Yep. That would mean the injector pump's not getting what it's supposed to and more prone to failure. "



I guess I'll be heading to Cummins.