Archived Intermittent lift pump at start

[BGott]

Howdy! I have a '98 Ram 2500, 24 valve ISB, 5 spd, 2WD. My problem is a long term intermittent that is getting to be regular. When I go to start the truck it doesn't want to cut the lift pump on. This used to be a hot start problem but will now do it at any time. You go to start the engine and it won't start, let off the key from start to run, wait 5 seconds and the pump cuts on, pressure rises and then the engine will start. When it first started screwing up back in January I checked the pump pressure and it was low so I changed the pump. The problem tapered off and then returned with a vengeance. I re- checked the pump and it had wildly varying presures so I hung another one, pressures are steady but I still have the starting problem. I've checked powers and grounds, all seem OK. When the pump cuts on there is instant pressure so I don't think I have a drain back problem. Truck had a PO1693 and a fuel sender code, the sender was broken way before the problem started so I doubt it's related. Snappy shows the pump is running when it is demanded by the computer, for what ever reason the computer is not cutting it on when it screws up. The engine starts instantly with fuel pressure and runs and drives well with good fuel economy. Anybody have this happen before?

 

[Jetson]

My "99 is doing the same thing. My transfer pump has been moved to the frame rail. It is powered through a relay. The relay gets the signal from the original pump connector and turns on the relay. I also thought I had a leak allowing the fuel to drain back, but I found out that if I turn on the key and wait, the fuel pump will eventually cycle and the truck will start immediately.



I found that if I turn the key off and then on and bump the starter to get the fuel pump to run, it still would not come on, but if I waited, eventually the pump would come on and run for 20 seconds or so.



I think it must be an ECM problem. I tried resetting the ECM, but it didn't help. I remember that HVAC's truck had a similar problem. He said the ECM would not turn on the fuel pump, so he wired up a relay that was triggered by a key on hot wire.



The ECM appears to go through an initialization process when the key is turned on. It just appears that process has slowed down or been corrupted.



Maybe Marco could help?

 

[BGott]

I talked to the ISB "Guru" at Cummins Southern Plains and he recommended at reflash, at $230. He said the programming in the ECM would corrupt over time. I would gladly spent the money if I thought it would do any good but I'm not going to let this be a gateway to my back pocket. I will probably go ahead and do it, the next step is opening up the computers and looking for cold solder joints.



Next question, what's the difference between the Dodge dealer's $76 reflash and the Cummins dealer's $230 reflash?



The wait period you mention before the pump cuts on, it wouldn't be exactly 5 seconds, would it? That's what it is on mine.

 

[ToolManTimTaylor]

Could it be?

Part of "No Start" diagnosis on vehicles equipped with VTSS should include a verification check of the power supply to the Central Timer Module (CTM). The CTM provides the Powertrain Control Module (PCM) with an "OK To Start" message via the CCD bus. If the message is not received by the PCM, the PCM will not allow the engine to start. Initially, the engine may start and stall but will eventually not start at all. Most CTMs are supplied battery voltage through the power door lock fuse. An inspection of the fuse should be one of the initial diagnostic checks performed. If the fuse is operational, a verification check of the communication system from the CTM can be performed using the DRBIII®. Attempt to communicate to the CTM. If the CTM does not respond to the DRBIII®, the DRBIII® will identify a "No Response From Central Timer Module" message. A "No Response From Central Timer Module" message may indicate that the CTM is not powered up. Please refer to the "Communication" section of the appropriate Body Diagnostic Procedures Manual to assist in "No Start" diagnosis due to communication problems from the CTM. In addition, the "Vehicle Theft/Security" section will aid in the diagnosis of "No Start" issues involving the VTSS system.

 

[Jetson]

I do not have a VTSS, so I don't think the timer module is causing the problem.

The wait period you mention before the pump cuts on, it wouldn't be exactly 5 seconds, would it? That's what it is on mine.

Okay, I used my stopwatch. It was 5. 03 seconds before the lift pump turned on.



The dealer reflash may just be an update rather than completely erasing and then flashing the ECM. $250 sounds high for flashing the ECM, especially if you don't really know if it will help. I wonder if he would guarantee that the lift pump would start up right away like it is supposed to?

 

[BGott]

I believe I read I read in Alldata that the ECM was flashable once, at installation, and that it had the capability to be updated. Unless there is a re- flash for this particular problem I can't see it helping. I think I'll wait until I've heard from one or two people that have had this problem fixed by a re- flash. I don't have a VTSS, either, so I don't think it's the central timer controller. I've been thinking about adding a relay, if I could find a relay that would trigger for one second activation I think I would try it. Adding a relay that ran the pump all the time whenever the key was on could cause problems. If you had someone sitting in the truck that turned the key to "run" to listen to the radio or to lower a window and left the key on it would probably burn up the pump.



About the only think guaranteed with the re- flash, I believe, is that they'll charge you a couple grand to find and fix the problem when the re- flash doesn't work.

 

[Marco]

That sounds pretty much like a corrupted flash data in the ECM. The delay before the pump runs, that is. Seen that several times.



Anyway, 200+ bucks for a software update is a "little" high.



On edit. Thinking about it. I've also seen a few ECM's with bad CPU's doing that exact same thing.



How's the WTSL working? Delayed too? Longer or shorter than usually?



Marco

 

[Jetson]

The WTSL is delayed just like the lift pump. What seems odd is that it works perfectly sometimes. Other times the lift pump and WTSL are delayed. This would make me think the computer is going bad and it is not just a corrupted flash program. If the program was corrupted, wouldn't the problem be consistent?



A year ago I had lost the WTSL, but after unplugging the batteries for a few hours, it came back.

 

[BGott]

I haven't even paid attention to the WTSL. I had to think about it for a while before I even knew what you were talking about. I might try disconnecting the batteries and see what happens. I'll do that tomorrow night, if something screws up I don't want it to be on a Sunday.

 

[R-N-R]

Disconnect the pos cables from both batteries for at least 20 min. , then turn your key to the on position and reconnect the batteries to reset your ECM.

 

[Marco]

Jetson,

the delayed WTSL light points towards internal ECM problems.

I've seen that caused by anything ranging from bad memory chips, bad ram up to bad CPU.



Marco

 

[BGott]

I haven't had time to mess with it the last few days. I have noticed, however, that whenever the lift pump is screwing up the WTSL is delayed. I guess I'll be hanging an ECM in the next few weeks. Thanks for the help!

 

[KLockliear]

I know this is an OLD thread, but mine is doing the same thing now. Just started last week.



Turn the key and the truck will start, but I show 0 fuel pressure. Shut the truck off, sometimes the pump will run the next time, sometimes not for a few key cycles.



Any other input on this?

 

[Jetson]

Is your Wait to Start light coming on immediately every time you turn on the key?



When mine started having problems I bought several more months of time by disconnecting the batteries for 30 minutes, then reconnecting to reset the ECM. My WTSL started working again for about 6 months.



I tried to have my ECM repaired, but the shop couldn't fix it. I bought a used core and they remanned that one. That was 2 years ago and still working fine.

 

[KLockliear]

Did the battery disconnect/ECM reset dealio yesterday. WTSL works as normal, but lift pump doesn't always come on.



Previously, anytime you bumped the starter, the LP would run for ~30 seconds. Now, not the case. After a few key cycles, it will come on and run fine after that, but if it's not running at startup, it won't come on later. I have to cycle the key and bump the starter until I see FP, then I can start it.



I'm thinking I'm going to do the ECM bypass on it, and put in a relay to run both pumps (I have a frame mounted pusher that currently gets power from a relay that is triggered from the stock LP power wire). Just have to figure out what wire to tap for the signal. Perhaps the Edge box wire is the one to do, since the turbo timer will keep the engine running after the key is off, and I want the pumps running then.

 

[JLandry]

Did the battery disconnect/ECM reset dealio yesterday. WTSL works as normal, but lift pump doesn't always come on.

Have you checked to see what voltage (if any) is present at the lift pump wiring harness when you bump the starter?



The reason I ask is because anther TDR member recently had a problem somewhat similar to your's, except I think his lift pump wouldn't work at all when he bumped the starter (even with multiple tries). Naturally he assumed the lift pump was dead so he purchased and installed a new one. It didn't work either!



Then he measured the voltage on the lift pump wiring harness (coming from the ECM) when the starter was bumped and found only 4 volts where it should be 12 or more. Since the lift pump is powered directly from the ECM with no external fuse or relay, it had to be an ECM problem. I should mention he also eliminated the wiring harness as being the culprit.



Before replacing the ECM, this TDR member disconnected and cleaned the pins of the ECM connector, then also removed the ECM, cleaned it and its mounting location on the engine block, then reinstalled it making sure it was well grounded (lock washers digging into metal).



That solved the problem! His lift pump worked perfectly after that.



Soooo... you might also want to remove the ECM to clean it, the connector pins, and its mounting location on the block. Can't hurt to try.



Good luck,



John L.

 

[KLockliear]

I know the lift pump works. I haven't checked for power at the pump, but since my pusher pump trigger wire is tapped into the power wire to the stock LP, that relay would trigger if there was power to the LP. It doesn't when the LP doesn't run. Seems as if the ECM isn't always sending the LP power.



I guess I will try the cleaning gig tonight before "hot wiring" the LP to a key on/Edge on source. Can't hurt, other than waste a little time.

 

[JAde]

Please keep us posted on your progress.



I have a 98. 5 that's been through 2 lift pumps and injector pumps since I bought it 2 years ago. I rarely use this truck (only 5k in 2 years) so it seems like I have to throw money at it every time I turn the key! Installing a fuel pressure gauge several months ago discovered the last set of pumps. A Smarty, injectors and a "built" trans are the only mods. I sure hope we can find a cure soon because this isn't the noted reliability I signed up for when I purchased this truck now refered to as the "Money Pit"!



Also - I just ordered an Air Dog 100 setup (MORE $). Can its relay be wired to a keyed 12 volt source? I haven't received the unit yet so I'm not sure. Obviously, if I connect it to the lift pump lead it would stand to reason that I'd have the same fuel pressure / no start problems I have now.

 

[KLockliear]

Put in my new pusher pump tonight. Immediately, the stock lift pump began working normally again. I will report back in a week or so, to see if that was just a fluke, or if all is good again.



Funny, the issue I had with the key FOB not locking the doors when the truck was running (or Edge Juice turbo timer working) mysteriously seems to have gone away too.

 

[Jetson]

The ECM doesn't send a full 12 volts to the lift pump when you first turn the key and crank the engine. It is supposed to step up to 12v after the engine cranks. If there were marginal electrical connections, they could cause more of a problem during the low voltage time.