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No fuel pressure but Fass pump is working.

the7t7
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the7t7

the7t7

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So I was driving around testing my new 7x.012 injectors and new quadzilla and my truck died. I tried restarting and it started right back up. Fuel pressure from my Fass seemed a little low (around 12 or or 13 psi) but otherwise everything seemed like it was working ok. I made a stop for about 20 min and when I got going again the truck died again 100 yards down the road and wouldn’t start. I noticed that the pump wasn’t cycling on key on/ starter bump so I had the truck towed back to my shop. When I tested the pump by putting 12v to it, it worked, so I replaced the relay with another but couldn’t get the pump to cycle. I then tested the ecm signal lead and I was only getting 6v at key on and nothing higher when I bumped the starter. I did notice that when I bumped the starter the voltage went to open line and then back to 6v. I don’t think 6v is enough to trip the relay. So do I have a bad ecm now?  This would really suck since I just replaced it with a reman from ACS. Any thoughts?

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Mopar1973Man

Mopar1973Man

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13 hours ago, Manimalmother said:

I just posted this same advice on the 911 forum yesterday, but may be applicable here.  While installing my injectors I knocked this connection loose on the cowl.  I had no WTS and no lift pump.  Check it to make sure it's nice and tight and the retaining clip is engaged.  

IMG_20190213_105347.jpg

 

Suggestion. Take that plate off and pull the plug loose from the plate. Now zip tie the plugs to the loom on the cowl. You'll find they move over towards the driver side a bit more. Then they are always out of the way. 

 

13 hours ago, the7t7 said:

I then tested the ecm signal lead and I was only getting 6v at key on and nothing higher when I bumped the starter. I did notice that when I bumped the starter the voltage went to open line and then back to 6v.

 

Lift pump positive lead yellow/white is from the ECM directly. The Black/White lead is grounded behind the starter. You might check the ground lead. Yeah you have to pull the starter out to see it even. you can test by red probe in the yellow/white and then black probe to battery negative. If 12V is present then the ground is most likely bad.

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the7t7

the7t7

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17 hours ago, Manimalmother said:

I just posted this same advice on the 911 forum yesterday, but may be applicable here.  While installing my injectors I knocked this connection loose on the cowl.  I had no WTS and no lift pump.  Check it to make sure it's nice and tight and the retaining clip is engaged.  

IMG_20190213_105347.jpg

I don’t believe I have that connector. Maybe 1998 wiring harness is different than 2001. My fuel pump lead seems so come directly out of the ecm, down and then up by where the fuel filter was. 

 

3 hours ago, Mopar1973Man said:

Lift pump positive lead yellow/white is from the ECM directly. The Black/White lead is grounded behind the starter. You might check the ground lead. Yeah you have to pull the starter out to see it even. you can test by red probe in the yellow/white and then black probe to battery negative. If 12V is present then the ground is most likely bad.

When I measured the voltage at the plug, I measured the y/wh wire with the red probe and the black probe was grounded on the firewall dash metal. So I didn’t use the bl/wh wire at all. I’ll try it again with different grounding to double check.

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the7t7

the7t7

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I get 6.5v no matter the ground on key on. It drops slightly as I bump the starter and then back to @6.5 v. Also no codes. I don’t even get the grid heater code I should be getting as I don’t have one. 

 

What about running a temporary relay to see if it runs? Isn’t there a relay mod for the fuel pump that doesn’t use the ecm. I remember seeing something about that in one forum or anothe. 

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dripley

dripley

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You could just put battety power to it first and see if runs properly. The bad thing with bypassing the ECM is you loose control of it shutting the pump down in case of a wreck and you are knocked out. If the fuel line ruptures the pump will keep pumping fuel untill you turn it off.

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Dieselfuture

Dieselfuture

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It should start and run without lift pump, as long as there isn't much load on the engine. I would not drive it anywhere without the lift pump, but I would not be scared trying to start it. On the other thought, Fass has gear rotor and I'm unsure if vp we'll be able to suck fuel through it. 

It kind of does point to the ECM

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Mopar1973Man

Mopar1973Man

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10 minutes ago, Dieselfuture said:

It should start and run without lift pump, as long as there isn't much load on the engine.

 

Yes, it's true it will start and run without a lift pump and drive at low speeds for safety yet. 

 

10 minutes ago, Dieselfuture said:

Fass has gear rotor and I'm unsure if vp we'll be able to suck fuel through it. 

 

So does the AirDog pump and it will still suck fuel through the pump and run. 

 

My last AirDog failure it locked the pump motor up and blew the fuse. ISSPro EV2 gauge dropped to zero and lit the fuel pressure warning light. I was at a traffic light and still running. Drove a short distance to a parking lot and left it idling and tried changing fuses to see the 20A fuse blew. I drove to a safe parking spot. Then made the phone call for a tow truck. During my 2 hour wait, I was still starting the truck and getting heat in the cab to keep MoparMom and myself warm. VP44 is still doing just fine. Since I keep 2 cycle oil in the fuel this keeps the wear stress down and allows me to escape the low-pressure problems easier. 

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the7t7

the7t7

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Yeah, I kind of think it may have been doing that all morning. It had trouble in the morning going into gear when it was cold. It kept cutting off so I let it warm up more than usual. I thought it was maybe my newish tune under fueling and/or not dialed in. I was just putting around town and it died once but started right up again. Now it won’t start. I’ll put some power to the pump and see if it starts tomorrow. If I have ecm issues then maybe other things will pop up when it’s running or it won’t even start with fuel pressure. I’m guessing ACS won’t warranty my ecm since I’m using a tuner?

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Mopar1973Man

Mopar1973Man

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29 minutes ago, dripley said:

I guess my next question would be what undue stress does a tuner put on the ECM?

 

Edge Products and Quadzilla ZERO impact. All it does insert commands on the CANBus with high priority and has no impact on the ECM. ECM has no clue the tuner is even there. 

 

Now Smarty or any flash tuner puts stress on the EPROM which has a finite number of times it can be flashed. Then if the flash goes wrong you can make a mess out of the ECM that requires reflashing or replacement. Smarty and SuperChips wipe out all the ECM software and reflash with completely different software. 

 

Addon...

 

Like my combo of the Quadzilla Adrenaline and the 7 x 0.010 injectors, this reduces the stress on the VP44. Being my idle engine load is about 13% and then my cruising 60 MPH engine load is only 17%. I'm not down to running Level 3 (No wiretap) which is the cleanest overall runs with the same power as stock injectors and Edge Comp with about 35 PSI of max boost. 

Edited by Mopar1973Man
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the7t7

the7t7

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Directly powering the fuel pump didn’t get the truck to start. So I hooked a tester to the fuel system relay signal wire (#1 or 85 lead) and I got 5.8 volts on key on and a little less running the starter. Shouldn’t that also be 12 volts to get the injection pump running? Does this confirm ecm as the problem?  A thing else I can test?

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