Engine/Transmission (1998.5 - 2002) !!!! p1693

[coreyallan]

In addition to my Fuel psi at start thread I would like to submit this further info about my most recient problem. I just went to the gym and was there for an hour and a half or so the truck was at running temp on the way there. I came back and parked the truck at running temp. I took a shower and went back out to start the truck and no lp psi, I tryed to bump the starter, no lp psi... . I opened the fuel bleeder and tryed to cycle the pump, no lp psi... I tryed to bump the starter again and no lp psi. Then, I tryed everything again at least once and no lp psi as a matter of fact the needle on my psi guage went in the oppisite direction when I cycled the key... . I checked for codes and got the companion code p1693. When the truck runs which is 99. 9% of the time it runs great and this is the first time that I said $%#! it and came back inside to talk to you guys... . help..... This is a saga, check out my other thread, "no start... no start... no start... start!

 

[coreyallan]

wow, man I have no idea whats going on here..... I read some threads and unhooked the batteries then reconnected them. I bumped the starter and got 10psi from the lp and she started up/ drove great... This was half an hour after my post...

 

[johncameron]

Could you hear your LP running when you had no pressure?

 

[AllianceDiesel]

1693 is a code that pretty much is just for communication between the ecm and the jtec module (your other major computer that looks at trans, speed, stuff non-cummins but powertrain), all it is, is that the jtec module is telling the ecm that there is a code in its computer



you have something else going on, I am working a double tomorrow and I'm up right now feeding my daughter so I won't have a chance to look at your other thread, but when I get off work, I will try to help

 

[SHobbs]

First thing would be to get the codes pulled. Most auto stores can pull them but they might not be able to get all of them. Try cracking the supply line at the VP44, bump the starter to cycle the L. P and see if fuel squirts out. No fuel then your L. P kicked the bucket Even if you hear the L. P running it can still not be pushing fuel.

 

[JLandry]

Corey,



I went back and reviewed your threads... how frustrating!



Before you spend anymore money on lift pumps and related upgrades, the next time this "no lift pump pressure" problem happens, I would quickly disconnect the lift pump wiring harness and connect a voltmeter to the vehicle side of the wiring harness to see how much voltage the lift pump is getting when you turn the key to run (should see voltage for 2 seconds) and then again when you bump the starter (should see voltage for 25-30 seconds). Better yet, maybe you might even fabricate a jumper harness to go between the lift pump and vehicle wiring harness to allow you to leave some voltmeter leads hooked up all the time in order to monitor the lift pump voltage from the cab. It might be interesting and help rule out the lift pump being the culprit.



I'm just wondering if you have an intermittent wiring harness problem (maybe a loose connection somewhere) between the ECU and the lift pump? If it turns out that the lift pump *isn't* getting power when this problem happens, then we can help you trouble shoot the wiring harness to find the exact location of the problem.



Best regards,



John L.

 

[coreyallan]

Thanx guys, alot of interesting suggestions. First, I dont think anything is loose it def seems to be a hot cold thing as far as when this occures much like the other threads with similar problems. The lp dose not run when I show no psi, I have confirmed that. When this happens one of my routines is to open the bleeder on the filter housing to confirm lp operation or not, although I can hear it usually. I will start to carry my multi meeter so when this happens I can check for voltage at the lp harness. One thing in case you didnt notice is the fact that when this happens nether a normal key cycle nor a starter bump will start the lp sequience... . Is there ever a time when the lp wont cycle for example like when the system has enuff pressure or somthing like that, this problem has been present so long that I cant remember if somtimes it dosent cycle... Lately I've got 10 +/- psi at cruz and +/- 5 at wot and like I said the truck runs like it should. . I will go and pull codes later and get back w u... Lets say I have some sort of an leak after the filter, I dont even know if thats common but just for argument sake. What if I plug the supply line to the vp and cycle the key to cycle the lp and check for leeks? It might show somthing between the lp and the vp? Dose that sound like somthing that anyone has ever done or would it even make sence?

 

[JLandry]

Is there ever a time when the lp wont cycle for example like when the system has enuff pressure or somthing like that

Corey,



No... the lift pump should always run for 2 seconds when you turn the ignition key to the run position, and about 25 seconds when you bump the starter. You should be able to repeat either of these cycles indefinitely.



If your lift pump is not cycling when you turn the ignition key to the run position or bump the starter, then either the lift pump is bad or there's something wrong with the wiring harness, or there's something wrong with your ECM. I don't have the wiring diagrams with me, but going from memory the lift is powered directly from the ECM... there are no relays or fuses in between. I can double check this tonight.

What if I plug the supply line to the vp and cycle the key to cycle the lp and check for leeks? It might show somthing between the lp and the vp? Dose that sound like somthing that anyone has ever done or would it even make sence?

I don't think that's necessary and plugging the fuel line between the lift pump and the VP44 might even be damaging to the lift pump.



I thought I read in another one of your threads that you had disconnected the fuel line at the VP44 and stuck the end in a bucket to check for fuel flow when you cycle the lift pump and you didn't get anything. That test confirms either the lift pump isn't working or the fuel line is plugged somewhere between the lift pump and the outlet at the VP44 (doubtful).



No... I think you've pretty much established the likelyhood that your lift pump is good (you've replaced it multiple times) but at times it's not pumping for some reason and you feel it could be related to engine temperature. I think the next step would be to verify if the lift pump is actually getting power when the problem occurs, and then if it isn't, we can start trying to figure out why... where the loss of power is occuring.



If you do find there is no power present at the lift pump harness, I would next check for power on the appropriate wire coming from the ECM. When I take a look at the wiring charts tonight in the Dodge service manual, I'll be able to tell you which wire(s) in which connectors at the ECM you should check. If it comes down to that, it would be easiest to have one of those voltmeter leads with a sharp tip so you can probe (pierce) the wire.



Regards,



John L.

 

[coreyallan]

Ok John, sounds like a plan. As you know there is a "fuel system relay" in the box under the hood but I dont know what components this services, I did replace it though as pm. Thank you for the help... I think these are great trucks but this fuel system and its associated components are totally frustrating. If I knew about all this $#@! b4 I bought it things might have been different... But now I have a 53 AND the hair raising fuel system..... What-a-ya gunna do... .

 

[JLandry]

As you know there is a "fuel system relay" in the box under the hood but I dont know what components this services, I did replace it though as pm.

Corey,



I'm 99% sure there's a fuse and relay in the Power Distribution Center marked "Fuel Pump" but that's for the VP44 injection pump. It's good that you replaced that relay as it can't hurt, but that wouldn't affect the lift pump.



Keep us posted and god luck!



John L.

 

[coreyallan]

I just went to Home Depot for some parts. I got in the truck which was cold from last night and cycled the key and no lift pump so, I cycled it again and got a continues cycle for 3-4 sec @6 psi and it started right up. I drove to Home Depot not more than a mile or two went inside for a few minutes and came back out cycled the key and no lp. I bumped the starter this time and got 10+ then started it up, it ran fine... .

 

[coreyallan]

Ok, now we're getting somwhere! I went to Autozone today to return an old carter lp I had and the clerk scanned for codes, came up with a p0336 (crank position sencer). I returned to the boat and got on here and found that made total sence... ... Mon I will get one, I dont think there is anywhere I can get one on sunday around here.