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So got a friends truck I'm working on, its a 98.5 24V auto 3500 dually. When I got it towed to my house I was told it stalled a few times and now would not start, cryptic I know.
Put key in and light on dash come on and turn key and nothing. Check batteries and cables and all look clean and tight. Went to starter and the exciter wire never gets power when key is tuned.....hmmm. Swapped relay in box under hood and no change. Jumped power to exciter post on starter and it turned over. So figured it was neutral/park safety switch. Checked it and wiring looked ok than found diagram and grounded the brown wire disabling the switch and same result, wont turn over. I then tried starting it in neutral and it turned over fine. Whatever its now turning over but wont start.
I hit it with a little ether and it fired right up. Now I know its fuel related. Checked around and the "lift" pump should be getting power when key is turned on and I have verified it is getting power but does not make a sound. So I think thats my 1st issue. Thoughts?
Now my reading sasy there are many issues with stock lift pump. Should I replace it with an after market one and if so which one?
I was watching this video on lift pump install and he said there are two electrical connections, the one on bottom a water separator 1:40 and than the large two wire connection on top 1:50 that was for a heater?? Im lost what powers this pump,is it not electrical? The wires I thought were for the pump actually the heater? If so how to I test the pump?
So as I learn........So what I thought was the lift pump was actually the fuel filter. So my testing for power to the pump was actually testing the fuel heater. Oh well live and learn. Is there a good way to test the lift pump? Is there a port to test pressure? Can I access the power to it wires anywhere easy to test them before I drop $$$ on a guess the pump is bad.
Turn key on and just bump starter, the pump should turn on and run for 45 seconds. Should pump 45 oz of fuel in 45 seconds. Read PDF file
Well I looked for lift pump and it was not under filter like everyone said it should be. Tracked down wires and they went to a relay that was just hanging three. Obviously not a factory install. The wires went down the frame rail. I jumped the relay and I can hear the lift pump..... It's in the tank???
I put a pressure gauge on one of the ports on the fuel filter and I can see 13-15 psi when pump is jumped on. But if I remove jumper and put back the way it was the pump only operates for a second when key is bumped and never gets pressure on the gauge.?
With lift pump jumpers on it I bled the 44 pump and injectors 1,3 and 4 and it started. So whats going on here? Why pump in tank? Who's put the relay and wires in for it? Looks like built harness but looks to be installed like teenager installes his 1st stereo. Can I just hook up pump to run when ever key is on and just lest it eat?
Pump in tank was a dealer modification under warranty or as a replacement for the stock LP if it failed.
The ECM has an output that controls the LP directly, with a 1 second run when the ECM is powered up, a 15 second run when the starter is bumped and the engine does not run, LP on full power while engine running, LP 50% PWM while engine cranking.
With a lot of aftermarket LPs the pump draws much more current than the ECM can supply and then the relays get installed.
Pump in tank was a dealer modification under warranty or as a replacement for the stock LP if it failed.
The ECM has an output that controls the LP directly, with a 1 second run when the ECM is powered up, a 15 second run when the starter is bumped and the engine does not run, LP on full power while engine running, LP 50% PWM while engine cranking.
With a lot of aftermarket LPs the pump draws much more current than the ECM can supply and then the relays get installed.
Just key on LP run is a bad idea..
So with a test light on ECM out put and only getting maybe 1 second when key on and not getting 15 seconds when starter is bumped it has to be a ECM issue. Right? I read somewhere that these ECMs go bad and had to be flashed.
Another question, should it hold pressure? With the 1 second bump and even with the 15 second run (if I jumper relay) soon as it goes off pressure bleads down. That an issue?
You said the relay was because the stock ECMs had hard time supplying the current needed....this relay could be just for that reason but it's done so badly, the power wire attached to battery has a 15amp fuse that is in line on maybe 20ga wire, *** thats wire never going to hold 15 amps even.
See some pump times and incorrect numbers here, so I'll do my best.
The lift pump will run for 1-2 seconds when the ignition is switched to ON (but not START) to ensure fuel to the injection pump. While cranking, the ECM limits power to the lift pump using pulse width modulation to limit pressure to the injection pump while trying to start the engine. After the engine is running, the ECM applies full power to the lift pump continuously. If there is a failed start attempt (or doing the bump the starter trick), AND the key is left in the ON position, the ECM will run the lift pump for 25 seconds to help prime the fuel system.
There is no relay for the lift pump, it is powered directly from the ECM. The fuel sytem relay is for the injection pump.
The OEM lift pump should be mounted to the engine block, below and behind the fuel filter. It's near cylinders 5 and 6. Your's may have been retrofitted by Dodge to have the lift pump relocated to the fuel tank. If you have the original style pump, it should look like this (fuel filter was removed for this picture):
To answer your other question, no, the system does not hold pressure when nothing is running.
You may have an in tank pump, or an aftermarket pump. Follow the fuel lines and see what you have.
See some pump times and incorrect numbers here, so I'll do my best.
The lift pump will run for 1-2 seconds when the ignition is switched to ON (but not START) to ensure fuel to the injection pump. While cranking, the ECM limits power to the lift pump using pulse width modulation to limit pressure to the injection pump while trying to start the engine. After the engine is running, the ECM applies full power to the lift pump continuously. If there is a failed start attempt (or doing the bump the starter trick), AND the key is left in the ON position, the ECM will run the lift pump for 25 seconds to help prime the fuel system.
There is no relay for the lift pump, it is powered directly from the ECM. The fuel sytem relay is for the injection pump.
The lift pump should be mounted to the engine block, below and behind the fuel filter. It's near cylinders 5 and 6. Your's may have been retrofitted by Dodge to have the lift pump relocated to the fuel tank. If you have the original style pump, it should look like this (fuel filter was removed for this picture):
To answer your other question, no, the system does not hold pressure when nothing is running.
You may have an in tank pump, or an aftermarket pump. Follow the fuel lines and see what you have.
Thanks.
The lift pump on clock was removed I guess and there is this aluminum block there to hook likes up to. The plug that is there that "used to" be hooked up to the lift pump now connects to a harness that has a relay in it that goes to battery, ecm, and fuel pump in tank.
I put a pressure gauge on filter block and the pump never stays on long enough to make pressure unless I power the pump on constantly. But if I do it builds 15psi and starts fine.
So I'm guessing the ecm is just not putting on the lift pump long enough to prime system, does this happen?
So got a friends truck I'm working on, its a 98.5 24V auto 3500 dually. When I got it towed to my house I was told it stalled a few times and now would not start, cryptic I know.
Put key in and light on dash come on and turn key and nothing. Check batteries and cables and all look clean and tight. Went to starter and the exciter wire never gets power when key is tuned.....hmmm. Swapped relay in box under hood and no change. Jumped power to exciter post on starter and it turned over. So figured it was neutral/park safety switch. Checked it and wiring looked ok than found diagram and grounded the brown wire disabling the switch and same result, wont turn over. I then tried starting it in neutral and it turned over fine. Whatever its now turning over but wont start.
I hit it with a little ether and it fired right up. Now I know its fuel related. Checked around and the "lift" pump should be getting power when key is turned on and I have verified it is getting power but does not make a sound. So I think thats my 1st issue. Thoughts?
Now my reading sasy there are many issues with stock lift pump. Should I replace it with an after market one and if so which one?
Thanks!
-Mike
One of my lift pumps that went out just went silent like yours. Which was freaky until I realized that's what it was (had a fuel pressure guage on the fuel filter housing so it was easy to spot). MOST of the time, my lift pumps would just put out less and less pressure until you needed to change them (I changed mine at around 5 to 8 psi),..but if the lift pump just doesn't turn on,..then there is an open wire in the lift pump itself. Other than mine,..yours is the only other one I know that did it that way.
Sorry, I didn't read all the posts... Apparently yours has been moved into the tank. So disregard my post,..I have no idea what's going on with your LP.
If you want an aftermarket pump, you'll first have to remove the intank pump and make the fuel tank module the way that it was before it got that pump.
My truck never had the intank pump. I had 2 OEM style lift pumps before switching it to a DDRP 5 years ago. The DDRP has run great since day one, and is still going strong.
The FASS DRP is a great option over the weak, stock lift pump. For the OP, I would take this opportunity to install a FASS Titanium with a sump pickup. I know its an expensive option, but my truck has never run better.
09-19-2017, 07:25 PM
