This is my first post and I have been looking around on here but haven’t found anything like my problem. I'm looking for any help. I have a 99 Ram 3500.  Some times when you turn the ignition switch on the wait to start light comes on and the lift pump does not but the truck will start immediately.  I checked the voltage at the stock lift pump connector and their is 6-7 VDC until the truck is started then it jumps to 12 VDC. Other times when you turn the ignition switch on the wait to start light does not come on and the lift pump does not turn on and the truck will crank but will not start.  After about 15-25 seconds the wait to start like and lift pump turn on and the the truck starts up and runs fine. I checked the voltage at the stock lift pump connector and theirs is 0 VDC until the wait to start light comes on.  I have no check engine light but have codes P0380, P1693, P0123, P1694.  The mechanic at the Transmission shop (after they rebuilt the transmission) tried a new TPS and said the new TPS did the same thing so they reinstalled the original TPS. He said the voltage at the TPS would steadily climb until it tripped the over volt then the wait to start light and lift pump would come on. He also thought it might be a bad ECM or PCM but wasn’t sure, but checked and cleaned all the grounds.  I found and repaired a shorted wire at pin 5 of ECM. I also sent the ECM out for repair and got it back today.  Before I installed the newly repaired ECM I completely cleaned all 4 battery connectors.  When I turned the ignition on the first time the wait to start light came on and the lift pump turned on for about 1 maybe 2 seconds so I bumped the starter and  the lift pump ran for about 30 seconds.  Then I started the truck, it started fine after letting it run for a minute.  Then I shut it down.  Then I turned the ignition switch on and had no wait to start light and no lift pump.  Then I bumped the starter and no lift pump but started fine.  I checked the codes and had P0380, P1693.  After some searching on here I found some stuff to check and found the Yellow/Black wire at the Intake heater relay disconnected reconnected wire.  I turned ignition switch on and no wait to start light and no lift pump cleared codes then cranked fine rechecked codes and had P0123, P1693.  Turned truck off, cleared codes, then turned ignition switch on no wait to start light and no lift pump but started fine and no codes.  I’m thinking I have an electrical glitch somewhere but not sure where to look next.  I’m thinking about ohming out every wire from the ECM to where they go. I want to check the connector at the TPS for corrosion and check all those wires.  I’m also wondering if my PCM might be messing up and if so could it have messed up my ECM again?  Any suggestions would be greatly appreciated.

Lift pump voltage is correct. it should be a modulated 50% duty cycle during cranking and 12V when running.

If the wait to start light is not coming on the ECM is not booting up. Basically brain dead. The first instruction typically is throw the WAIT TO START light and then check IAT temp and grid heaters. If no wait to start light then there is internal memory issues in the ECM and never complete its boot up process.

As for what might be messing up the ECM is the alternator. If the alternator is creating excessive AC noise it will kill the ECM.

Here is the engine wiring...

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/26-engine-systems/87-dodge-ram-turbo-cummins-24-valve-engine-wiring

 

The no WTS light and lift pump not working is pointing to an internal ECM problem. The ECM controls those functions. The weird thing to me is typically with that issue the truck will not start until the WTS light illuminates. If I read your post right yours starts whether the WTS is on or not.If the truck is warm and it is warm outside the WTS light will only illuminate briefly and you can miss it if your not watching closely.  Is your TPS oe style or after market,Timbo Apps?

 It would help if you would go back to your profile and fill out your signature with info on your truck. Year, auto or manual any mods you have done and such. Look at the bottom of my post and you can see what I am talking about.

TPS is stock sorry haven't figured out how to make a signature yet. I have an Edge Juice with CTS, Air Dog II 165, MBRP 4" Exhaust, and K&N Air Intake.  Everything thing else is stock for now.  The strange part to me is once the truck starts it runs perfect no issues at all.  This morning when I went to start it the WTS light came as it should but the lift pump kicked on for less than a second and the truck started fine. The pump should run for about 10 to 15 seconds when you turn the ignition switch on. My big concern is if I'm gonna do damage to the VP44 with the lift pump not always coming on like it should.  I just got the ECM back yesterday from a repair shop and the truck is about 90% better.  I'm only having the WTS and lift pump issues, all the other issues have been resolved with the ECM repair.  I also checked the codes this morning and didn't have any codes.  What ever it is causes these issues is intermittent and changes almost every time you go to start the truck.  Thanks again for the help. 

Here is the link for signature for you...

http://forum.mopar1973man.com/settings/signature/

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The pump should run for about 10 to 15 seconds when you turn the ignition switch on.

Not really. Some software don't have a lift pump signal at key on and other like mine only have 1 second burst.

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My big concern is if I'm gonna do damage to the VP44 with the lift pump not always coming on like it should.

That's why you watch the fuel pressure gauge after starting. If the pressure is between 14-20 PSI then you fine. At key on doesn't count.

Also any time your testing for the WTS / Lift pump you must leave the key OFF for at least 5-10 seconds for the ECM to shut down. If you cycle the key too rapidly then the previous booted software is still use because it never completed so you might not see a lift pump burst or a wait to start light.

So when they repaired my ECM they may have loaded a software that only turns the lift pump on for a short burst?  Before these problems started it would run for a few seconds so I figured the burst was wrong.  Thats good info to know.  I have noticed in the last day or so the WTS light is always coming on.  The lift pump turns on for short burst most of the time.  The times when it doesn't kick on their is a weird noise not real loud but kinda like a buzz or rumbling noise.  When you hear that noise the lift pump doesn't cycle on but the truck still starts.  I'm thinking about not worrying about it anymore lol. I'm not sure if their is a real problem or if I'm being to nit picky.  Thank you for the good info and help