My truck recently started dying while driving, or failing to start when hot. It seemed like it fit the symptoms of a failing IPR. I never could reproduce the failure while it was hooked up to AE.

I just replaced the IPR and now I can't get it to start. In the process of the IPR swap, I removed the fuel bowl, replaced the fuel bowl o-rings, and the fuel/water separator filter.

At first, it seemed like the fuel pressure was really low (I was only seeing 20psi). After several tries, the fuel pressure seems to climb now to 55-60psi (like it did before the repair). I can feel the fuel pump under the driver-side rail buzzing and it seems to be doing its job (it is probably the original pump). AE shows injector pressure numbers that seem to be healthy (While cranking: 2200PSI Injector control pressure, 2.85V at ICP, 36% duty cycle). The HPOP is full of oil.

My suspicion was originally the electric fuel pump. The pressure numbers don't quite seem as stable as they used to be. But I'm not convinced. The pump is definitely working and the PSI numbers seem reasonable at this point.

Any suggestions on what to try next?

 

I would say cranking voltage or oil level, but I'm actually leaning towards the fuel bowl stand pipe this time after your rebuild

 

Cranking Voltage: The batteries started getting tired so I jumped it with our other car. It didn't make a difference. I'm going to put a charger on the batteries today.

Stand Pipe: What can I check here?

Also the engine oil seems good. It has about 2500 miles on it, it shows full on the dipstick, and I see oil about 1" from the top of the HPOP.

 

Good call on the batteries.

The standpipe in the middle of the fuel bowl under the filter is spring loaded and has slots in it. The slots must line up or fuel flow will be restricted or cut off entirely.

Is your fuel pressure reading before or after the filter?

 

My fuel pressure is measured after the filter, down on the passenger side of the fuel bowl near the out-lines to each head.

 

Yeah that's what ya get for doing maintenance above and beyond what was required.

Pull the harness off the ICP sensor and see if it has oil contamination. That would indicate a dying or dead ICP. I say this because IIRC the default ICP value the PCM puts out when the ICP is dead is 2200 psi. Do those values change?

Any SES or codes?

OE Ford or IH IPR? Harness to it looks solid?

 

I'd install the old IPR.

 

Ha Ha. You sound like my father-in-law!

I replaced the ICP a couple of weeks ago when the truck first started dying. I thought that had fixed the problem... but that only lasted a couple of weeks before it started dying again. The replacement ICP is an OEM Motorcraft part. There was a little bit of oil in the connector before I did the swap.

I also replaced the CPS (with a motorcraft) around the same time. When I did the CPS swap, it didn't seem to make any difference in the symptoms that I was seeing.

I do see the injector pressure numbers changing while cranking: 2212.81, 2200.37, etc.

I tried charging the batteries. So far, no real change in the no-start situation. The fuel pressure numbers look better now, the gauge pops up to the 55-65 psi range pretty quickly where it didn't before. Still, it seems like something is missing, the engine hasn't even hinted at catching yet.

My plan today is to hook up AE again to see if I can see any codes or anything fishy. Will an injector buzz test tell me anything? Maybe one of the wiring harnesses got bumped loose or shorted somehow during the ICP install? Then I'll check fuses. Maybe try unplugging the bowl heater? I am able to talk to the truck with AE, so that means that the PCM is getting power doesn't it? After the fuses, I plan to inspect all of the nearby wiring harnesses in the valley.

Worst case scenario, I'll pull the fuel bowl back off and start over. Maybe a piece of an old fuel line o-ring got lodged in a fuel line to the injectors? (seems unlikely). I do still have the old IPR that I pulled, I suppose that I could try to swap that back in as well...

 

Hmm. Couple crazy thoughts as I'm nodding off here after work.

1. Oil level?
2. IPR installed in correct order? Tin nut is obvioysly last, preceded by spacer, after the solenoid, and first obviously the main valve body?
3. IPR got the correct pigtail reattached right? 2 connectors are the same and can reach both sensor plugs, but are different colors and will cause a no start if plugged in wrong. Too tired to remeber which they are tho, someone will chime in

 

I checked all of the mini fuses and they seem good. I also tried unplugging the fuel bowl heater and that made no difference.

I tried running the injector buzz test and heard zero buzzing. The tach moved, but no buzz was heard. AE reports the following error: P1668 PCM/IDM Communications Error after the test.

 

Hmmm, check to see if the connector to the IDM has come loose. Also check the connector to the PCM at the firewall but I doubt that is your issue based on your progression of symptoms. After that, Ohm out the harness from the IDM to the engine. Someone on here has a good diagram of that. I'll look for it.

 

I just checked the resistance to each injector at the 42-pin connector. Here is what I see:
Driver Side (all measurements in Ohms):
8: 17.3
6: 10.9
4: 7.7
2: 6.8

Passenger Side
7: 4.1
5: 3.8
3: 3.6
1: 4.0

For future reference, here is the pin-out that I used for the measurements: https://www.ford-trucks.com/forums/1...l#post15063915

I wasn't even able to get a reading on #6 until I wiggled the connector on top of the valve cover on the driver side. All of the driver-side numbers look high right? It looks like I might pull the driver side cover and see how the harness looks inside. $.50 mod time?

 

Yup, that's the diagram I was talking about. Your driver side readings are all high. 1 and 7 on passenger side look marginal. That still doesn't explain why there's no buzz at all though.

It is definitely time to go over your UVCHs and engine harness with a fine tooth comb. The connectors that connect to the UVCHs are also prone to cracks in the wires and contact fatigue.

Here's a chart with expected resistance values.

 

Thank you for the ideas and diagrams so far!

I have pulled both valve covers and re-seated the UVCH's. I did the $0.50 mod while I was in there. The resistances at the 42 pin connector now look quite a bit better:

Driver's Side (all measured in Ohms):
8: 3.0
6: 3.1
4: 2.9
2: 2.9

Passenger Side:
7:3.6
5: 2.9
3: 3.0
1: 3.0

I re-connected the 42 pin harness and pulled the connection from the IDM and did the tests recommended by FordTruckNoob AT THE IDM HARNESS and see the following:
TEST 1
Driver Side:
8 (Pins 23 & 9): 3.0
6 (Pins 23 & 19):3.3
4 (Pins 23 & 7): 2.9
2 (Pins 23 & 22): 3.2

Passenger Side:
7 (Pins 24 & 20): 3.5
5 (Pins 24 & 8): 3.0
3 (Pins 24 & 21): 3.3
1 (Pins 24 & 6): 3.6

TEST 2
Left bank power feed to ground: Measured Open
Right bank power feed to ground: Measured Open

TEST 3
Left bank power feed to Injector Ground Shield: Measured Open
Right bank power feed to Injector Ground Shield: Measured Open

The connector at the IDM looked good. No sign of water damage or anything strange. I also pulled the IDM out from under the wheel well and it also looks good. No sign of water.

I ran another Injector Buzz test and still I hear no injector buzz (no surprise really) and get the same P1668 PCM/IDM Communications Error. Is this looking like a dead IDM?

I still need to inspect the entire length of the harness from the IDM, to the injectors.

 

Yeah, I think your IDM is dead. Sorry.