6.9 IDI endless hard starts

[IDIBRONCO]

The next step might be to install a fuel pressure gauge to see what kind of pressure is getting to the IP. If you want to that is. I did this and it helped diagnose a bad IP because the pressure would start out high and then drop to nothing after a short time of driving. I installed an Autometer electric gauge with the sender before the factory fuel filter that's behind the alternator. That way, I can watch the pressure while I'm driving.

 

[seanres]

I'll take a look this weekend. If I find that my $1100 rebuilt IP turned to junk immediately I will not be a happy camper

 

[IDIBRONCO]

I feel like a fuel pressure gauge is a must have now. I recommend it to anyone along with a vacuum gauge to keep an eye on your vacuum pump.

 

[MadMac]

@seanres - I would chase @IDIBRONCO's suggestion of a fuel pressure guage. Borrow one if you can... The things left on my checklist are: Lift Pump... And then - a head gasket or much worse.

If you have not tested for Blowby, compression, and/or done a leakdown test - I'm guessing now is the time. Entirely possible I missed that part of the discussion...

Thx for the photo in response to my how is it... very nice!

 

[seanres]

Ran the truck today with ether, even with ether it was a super hard start despite the super strong cranking! Idled with a lope till it warmed up, and as it warmed up it had more white smoke which I'm not sure what to make of it. There was also barely a trickle of fuel from the IP return line, it didn't fill up the clear part even after idling for ~45mins.

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I ordered a T and fuel pressure gauge for the outlet of the fuel filter housing and will pick up a compression tester to see if that reveals anything

 

[seanres]

Got around to installing it. Fuel pressure at a constant 5 PSI at inlet between fuel filter and IP.

I also tried running the truck without the IP return line check valve and with the return line disconnected from the tank and into a bucket after the cross fitting at the back of the engine. Not turning over at all even with wicked crank speed, just a bit of smoke.

I'll be running the compression test tomorrow and let you all know how it goes, but my guess currently is compression as I've run out of ways to check the fuel system besides ripping it all out

 

[Old_F250_IDI]

My compression tester for 6.9 fits in place of glowplug so no need to remove injectors, but fuel supply needs to be stopped, otherwise it may damage the gauge if the cylinder being tested fires.
If I remember right (it's been a long time since I measured my 6.9 compression), I just disconnected power to the fuel shutoff solenoid.

 

[Noiseydiesel]

I will throw my two cents in here.
I believe
the Return fuel line from the top of the fuel filter housing to the fuel rail should be deleted as it might cause drain off.
Somebody else should feel free to chime in here.....

 

[seanres]

My compression tester for 6.9 fits in place of glowplug so no need to remove injectors, but fuel supply needs to be stopped, otherwise it may damage the gauge if the cylinder being tested fires.
If I remember right (it's been a long time since I measured my 6.9 compression), I just disconnected power to the fuel shutoff solenoid.

I finally got to testing it after having issues with a crappy Harbor Freight tester. Here were my results:
1: 400ish (forgot to record exact number)
2: 340
3: 420
4: 450
5: 420
6: 450
7: 400
8: 450

Some of the readings I stopped before totally maxing out the pressure just thinking that if its over 450 its probably fine, but after reading the bulletin I am thinking of going through it again to see if I can get more accurate readings. #2 seems to be a concern though so I think I will remove the valve cover and see if I can find anything wrong with the valves but that will be a first for me. Any other thoughts based on these readings?

 

[IDIBRONCO]

#2 seems to be a concern

Technically yes, but that's still an excellent reading.

 

[seanres]

Technically yes, but that's still an excellent reading.

That was my thinking, but that still leaves me more questions as to whats causing my issue if thats not the source. I have not checked the timing gear alignment and maybe that is one tooth off?? I am also thinking of just advancing the injection pump more to see if there is any difference with starting up until its around 3 dime widths advanced but not sure if theres any downside to doing that

 

[IDIBRONCO]

None that I can think of. Well there is one. You might have to loosen the injector lines on the IP. Once you do that, you can advance it all the way if you want to.

 

[seanres]

Found the fix that I've been searching for. Turns out that the pump gear was TOTALLY misaligned.. much more than one or two tooth from the markers. After correctly aligning everything and bleeding the air she runs like a top. Cranks for half a second with glow plugs and below 40deg. Needs some better fuel and a little bit of a tune up with timing and fuel amount, but I actually have a running truck that doesn't stall when I turn the steering wheel. Not even sure how it was able to run before.

It was not bad at all to align the marks. In case anyone else needs to do this, I aligned the harmonic balancer mark with the lower hole position for measuring timing and removed the gear pump housing with the IP attached and disconnected the fuel lines. I first felt the 0 mark which feels like a hole, so I had to turn it another 360 deg to feel the Y which feels very shallow using an L shaped pick. I marked the top of the two teeth besides the marked valley with a sharpie, then after removing the IP and pump gear cover I could align everything super easily. Then just reassemble the gear cover and IP and good to go.

Having some backfires and white smoke at high RPM. Will leave an update if I find any good ways to take care of it but my big issue is solved!

 

[IDIBRONCO]

so I had to turn it another 360 deg to feel the Y

That would be 180*. 360* would bring you back to the 0 again.

Not even sure how it was able to run before.

I haven't seen it with a 6.9/7.3, but I have seen a 6.2/6.5 run with the pump gear 180* out of time. They don't run well, but they will run.

 

[seanres]

I was turning it from the crank, I think the ratio is 2:1. So a full rotation from the mark on the harmonic balancer is 1/2 rotation of the cam gear. Either way I did feel a difference in the timing marks.

Interesting, it ran but super low on power and died when I'd turn the steering wheel without giving it any gas, same for going into gear. Now I can crawl in 2nd without any throttle no issue.

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