Lift Pump Delay

[Texas CTD]

I've been having an issue with the lift pump not doing the prime cycle when the key is turned on.

Every other time the key is turned to the "on" position, it will take 5-6 seconds for the lift pump to do it's 2 second prime. Once the truck is actually started, the pump runs fine and acts normal. 

 

If I try to start the truck once the key is on, and before the pump has ran, the truck will not start, it just turns over. If I immediately turn the key off after cranking, then the pump will run for 25 seconds, even after a the key is off.

 

I'm running a FASS HPFP, and this issue started about a year after I installed the new system. I've checked connections, and all seems to be good. 

When the key is turned, and the delay happens, the FASS relay does not click, so that tells me (most likely) the ECM is not triggering the relay. I did some reading, and it seems like a fairly common issue, and most people say the ECM is at fault, and the best thing to do is make a new circuit and put the pump on a switch.

 

Although, the truck should start without the 2 second priming sequence, if the fuel system is staying primed. (like with a mechanical pump) So I'm in the process of tracking down any fuel leaks.

 

I also thought about excessive AC noise causing this?? Possible... But my meter doesn't read low enough to test it.

 

Any opinions, or anything else to test?

 

[notlimah]

I think before I went and started pointing fingers at the ECM, I'd check/replace that relay and see if maybe that's the problem. 

 

When you say every other key on do you mean like first start up of the day and it's fine, then next start up there's issues then after that problems again? 

 

What fuel pressures are you seeing? What's your fuel level when the pump won't prime? Is the same delayed start more pronounced parked nose uphill? Better pointed down hill?

 

Your truck should start fine even without that prime. Mine seems to not do the 1-2sec *brrpp* prime when my fuels 1/4 and below but still always starts right up. I put a full tank of fuel in and it primes again.

[dripley]

Is your WTS delayed also? That would be another sign pointing to the ECM. From your description it does sound more electronics related than mechanical. Never hurts to check some of the simpler mechanical stuff though.

[Texas CTD]

8 hours ago, notlimah said:

I think before I went and started pointing fingers at the ECM, I'd check/replace that relay and see if maybe that's the problem. 

 

When you say every other key on do you mean like first start up of the day and it's fine, then next start up there's issues then after that problems again? 

 

What fuel pressures are you seeing? What's your fuel level when the pump won't prime? Is the same delayed start more pronounced parked nose uphill? Better pointed down hill?

 

Your truck should start fine even without that prime. Mine seems to not do the 1-2sec *brrpp* prime when my fuels 1/4 and below but still always starts right up. I put a full tank of fuel in and it primes again.

 

1 out of every 2 key cycles, (on average) it will delay, regardless if it's the first one of the day, or I've been running it all day.

 

20 PSI idle, minimal drop up to WOT. Filters are fresh.

 

No difference at different fuel levels.

 

I haven't done enough testing to see if it changes whether it's up hill or down hill... Working on doing that.

 

 

 

 

1 hour ago, dripley said:

Is your WTS delayed also? That would be another sign pointing to the ECM. From your description it does sound more electronics related than mechanical. Never hurts to check some of the simpler mechanical stuff though.

 

WTS acts normal.

[JAG1]

I like the switch idea instead of getting into a rebuilt ECM that can be a real headache getting a reliable one. A momentary switch you push at start up and then goes off after you let off would be a good way to maintain the safety feature. If you ever get into a wreck the L/P will still shut down like it is supposed to by the ECM..

[Me78569]

have you checked the relay for your pump to see if it is "sticky"?

[JAG1]

I don't think it is the relay because he does say it works flawlessly after start up and running down the road.

 

Unless there is a poor connection having to do with the 2-3 second lift pump activation side of it.

[Me78569]

that was my thought.  I had a relay that would take a couple extra second to flip due to grime inside the relay.  It got worse and worse until it finally stopped engaging.  

[notlimah]

I think if anything I'd talk to fass and see what they say. I bet you could convince them that they need to send you a new relay! 

[dripley]

If you  are lucky the relay in the Fass might be the same as the ones in the PDC  and you could swap and see it the problem persists or moves with the relay.

[Me78569]

Yea it should be just a standard 4 pin relay.  easy to swap it with another one and see if the issue goes away.  

 

[Texas CTD]

I did some poking around with a test light, and found the issue still occurring at the factory lift pump harness, with the FASS harness unplugged. So I think that rules out any FASS issues? I took several videos while testing, so I will try to get those posted soon. 

 

The hard start baffles me. Hopefully the video works, and y'all can see what I'm talking about. Judging by the symptoms, you'd think there's a bad loss of prime, but I haven't found a leak yet.

 

 

I did some poking around with a test light, and found the issue still occurring at the factory lift pump harness, with the FASS harness unplugged. So I think that rules out any FASS issues? I took several videos while testing, so I will try to get those posted soon. 

 

The hard start baffles me. Hopefully the video works, and y'all can see what I'm talking about. Judging by the symptoms, you'd think there's a bad loss of prime, but I haven't found a leak yet.

 

VID_20160711_145305.mp4

 

I'm uploading these backwards. This next video below was taken before the video posted above.

 

VID_20160711_145140.mp4

Edited July 11, 2016 by Texas CTD

[Me78569]

if the ecm is not supplying 12v on start them there is nothing to blame but the ecm as far as I know.

[notlimah]

Can't watch the videos right now but if your wondering about it being a leak park nose up a decent hill and let it sit overnight and see if the problem is the same or worse. Then park in the exact same spot again except the other way around. If it fires right up when pointed down hill that indicates a leak in your return fuel lines somewhere. It'd be worth trying to at least determine if that's a problem or not.

 

Did FASS even give you new wiring with relay for the that pump? Or does it just use the factory harness? Was there power at the factory harness?

 

Have you talked to FASS about this issue?

[dripley]

I am assuming that you are getting no power from the ecm to trigger the fass relay until you see the pressure move. Does this repeat itself on the next start? By that I mean not letting it sit for long. If you were losing prime and not seeing any fuel leaking, it would take a while for it leak down.

 I am definitely not the electronics expert around here but I would think at key on and the ecm boots up that it is looking for signals from many sources for engine start up. I would think that seeing that the lift pump is operating would be a prime issue for start up. 

[Texas CTD]

3 hours ago, Me78569 said:

if the ecm is not supplying 12v on start them there is nothing to blame but the ecm as far as I know.

 

That's kinda what I was thinking.  

 

2 hours ago, notlimah said:

Can't watch the videos right now but if your wondering about it being a leak park nose up a decent hill and let it sit overnight and see if the problem is the same or worse. Then park in the exact same spot again except the other way around. If it fires right up when pointed down hill that indicates a leak in your return fuel lines somewhere. It'd be worth trying to at least determine if that's a problem or not.

 

Did FASS even give you new wiring with relay for the that pump? Or does it just use the factory harness? Was there power at the factory harness?

 

Have you talked to FASS about this issue?

 

I'm working on getting the videos on YT. I uploaded them here from my tablet first.

 

I need to do that, and see if there's a difference up hill or down hill.

 

Yes, it's a complete kit from FASS, but the FASS harness plugs into the stock harness, so it gets triggered by the ECM. Power was intermittent at the stock harness' plug. I still have a video to upload showing that, so bear with me.

 

And I have not contacted FASS yet.

47 minutes ago, dripley said:

I am assuming that you are getting no power from the ecm to trigger the fass relay until you see the pressure move. Does this repeat itself on the next start? By that I mean not letting it sit for long. If you were losing prime and not seeing any fuel leaking, it would take a while for it leak down.

 I am definitely not the electronics expert around here but I would think at key on and the ecm boots up that it is looking for signals from many sources for engine start up. I would think that seeing that the lift pump is operating would be a prime issue for start up. 

 

I'm not sure if I fully understand what you mean, sorry. I randomly get intermittent power from the ECM while key is on, but when the truck is running, it powers the relay/lift pump just fine. Hopefully when I get these videos up it can give us all some better understanding. 

[Me78569]

you might probe the lift pump wires from the ecm to the plug looking for breaks / shorts etc.

[Texas CTD]

Here's a video. 

This was after about 10 lift pump prime cycles in the previous half hour or so while I was testing for power, and literally seconds before I shot this video, the truck was running, so i find it hard to believe it's losing prime that fast. Still possible, but very confusing.

 

https://www.youtube.com/watch?v=m8YgBzaU8PQ&feature=youtu.be

Edited July 12, 2016 by Texas CTD

[dripley]

3 minutes ago, Texas CTD said:

Here's a video. 

This was after about 10 lift pump prime cycles in the previous half hour or so while I was testing for power, and literally seconds before I shot this video, the truck was running, so i find it hard to believe it's losing prime that fast. Still possible, but very confusing.

 

https://www.youtube.com/watch?v=m8YgBzaU8PQ&feature=youtu.be

That is what I was trying to ask you. Couldn't get the words out right though. No way it is loosing prime that quickly.

[Dieselfuture]

I had this happen a few years ago, I was playing with a relay for the air dog when it was on before I swiched to fass, but I don't think it had anything to do with air dog as it still ran great after that day. What I did was unplugged the relay and used a jump wire to power lift pump directly just to see if would run that way incase I ever had to hot wire it. But I also tried starting the truck without a relay and not jumped and that's when I ran in to same issue, Truck won't prime and just keeps on spinning without a start. It ended up starting after abusing starter for a while and never did it since. So to this day I'm not sure if ecm got confused or what but I'm hopping I didn't do anything serious to it. Been about 3 years now. Not really an answer but this shi.. does happen for some odd reason.