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Old 11-21-2007, 11:50 AM
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power loss...

Hi all. I have a 86 f250 4x2 srw xlt blah blah... with a 6.9l IDI. Recently, Ive had a massive power loss issue (as if it had much to start out with...), so I ran a comp test. All the cylinders came back between 315 and 350 psi (good I assume?). The vehicle also has hard (very hard, like 20 minute) starts, stalls after starts, etc... (ooh, and lots of smoke.) I think its a fuel problem, but don't really know where to start. Any ideas? Thanks.
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Old 11-21-2007, 12:02 PM
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First, bleed any air that may be in the system by pressing in the Schrader valve. Hold a rag over it to keep fuel out of your eyes. Check the fuel pressure. It should be betwee 3 and 5 psi. Make sure the filter is good or replace it. Make sure all of the fuel and injector lines are tight. You may have an injector pump going south.
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Old 11-21-2007, 03:05 PM
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hrmm... ok, ill try those and get back to ya with the results. Thanks for the quick response
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Old 11-21-2007, 08:06 PM
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Sounds like an injector pump getting ready to quit to me! I had a 6.9 act like that with the smoke and power loss, but the power went pretty quik. I dont know why you are haveing trouble starting it, I would check all the glow plugs with a test light, one bad one and it will start slow and have a lot of white smoke from that cylinder. I also have a 7.3 who's pump is getting old and tired and it looses its prime over night sometimes and I have to bleed it to get it started. It will start but then die and act like it is out of fuel, but bleeding it will get it started. I am sure no mechanic just a guy who has put a whole lot of miles on these trucks and has to trouble-shoot stuff all the time, but I am learning more every day! I love this site! Good luck!
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Old 11-25-2007, 05:55 PM
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When you say "bleeding it" ...

Your description of running fine until it sits overnight, then starting up only to die almost immediately, sounds like the exact problem I'm having with a 1986 F-250, 200K miles, and new injector pump less than 50K miles ago.

I'll look tomorrow, but if I can't find a schrader valve on my fuel filter, or if opening it that doesn't bleed where the air is trapped, there some other bleeding point? Or do you just crack open each injector connection one at a time?

I'm also wondering if the loss of prime is from a bad lift pump rather than the much more expensive injector pump (or does this not have a lift pump?).

Any thoughts are greatly appeciated.
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Old 11-26-2007, 10:22 AM
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Thanks for the thoughts, heres what I know:
-There is a schrader valve on the fuel filter. When I have to bleed the thing, I bleed both the schrader valve and each injector line at the head. This gets it going again.
-I replaced a mechanical fuel pump, which resides on the lower passenger side of the block. This fixed nothing. There is also another pump looking thing on the drivers side under the hood, close to the door hinges (I should probably take a picture, as thats a terrible description.) If its a pump, it should be making some sort of humming noise while running, but it doesnt. Do you have any idea what this thing is?
out of curiosity, how much did your injector pump cost?
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Old 11-26-2007, 04:21 PM
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Here is the aforementioned mystery part, located to the right of the master cylinder:
www.agcomptec.com/f250/DSC00569.JPG
www.agcomptec.com/f250/DSC00568.JPG
Does anybody know what this thing is? (theories from friends include fuel pump, fuel strainer, water separator, etc...)
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Old 11-26-2007, 07:41 PM
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Quote:
Originally Posted by gweeds View Post
Here is the aforementioned mystery part, located to the right of the master cylinder:
www.agcomptec.com/f250/DSC00569.JPG
www.agcomptec.com/f250/DSC00568.JPG
Does anybody know what this thing is? (theories from friends include fuel pump, fuel strainer, water separator, etc...)
I do know what that is!!! It is the water in fuel seperator. Only the 6.9's had them here, the 7.3's are incorporated into the bottom of the fuel filter. If I remember right you dont want to use it too much because it will start leaking. I think bleeding it with the valve stem and cracking the injectors is the only way to bleed the system. Anyway, there might be a fuel pump on the frame too, cant remember, seems like we had an '85 that had problems with something on the frame. Good luck!
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Old 11-26-2007, 07:53 PM
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Quote:
Originally Posted by l'il diesel View Post
Your description of running fine until it sits overnight, then starting up only to die almost immediately, sounds like the exact problem I'm having with a 1986 F-250, 200K miles, and new injector pump less than 50K miles ago.

I'll look tomorrow, but if I can't find a schrader valve on my fuel filter, or if opening it that doesn't bleed where the air is trapped, there some other bleeding point? Or do you just crack open each injector connection one at a time?

I'm also wondering if the loss of prime is from a bad lift pump rather than the much more expensive injector pump (or does this not have a lift pump?).

Any thoughts are greatly appeciated.
It is my personal opinion that this ULSD we have to use is the reason we are having trouble with our injector pumps. I know a guy with a 12 valve cummins having the same trouble and he thinks something in the pump has been compromised by this diesel. I have had personal experience with it eating a rubber gasket one per week just like acid!!!! As far as bleeding it I would just stick to the valve on the filter. I have had bad luck cracking injectors to bleed them, I end up damaging the return lines or the injectors and I don't think it does any better job than the valve, just my opinion though. There is a mechanical fuel pump on the pass. side of the motor(front), I personaly have never had a problem with one. I think I am just going to have to get a new injector pump, I see them on E-Bay pretty reasonable. Let me know if you find a diff. fix!
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Old 11-27-2007, 06:50 PM
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To gweeds and powerstrokes only

I'm not real swooft on chat response, so bear with, but let me quickly answer one of the questions posed: the injector pump ran about $300 (can't recall if it was parts plus labor or parts only). Tried installing it myself in round #1, but in the end it would barely start or limp to the shop. Something about correct injector timing being easy to lose. I didn't believe a diesel could run so poor - smoke, no power, just miserable - was pretty sure it was ruined.

The shop mechanic got it back to running beautiful, but I never figured out exactly what I'd done wrong (altho I have a vague recollection of exposing a fairly large timing gear in front of the valve cover and maybe even taking it out).

I'll look for the 'other' fuel pump tomorrow - I'm still wondering what the fix is even if bleeding the fuel lines gets it started. This sure came on fast.

Just an afterthought and for what it's worth, if you're wondering what made me replace the injector pump - there was billowing blue/black smoke seen in the mirror going downhill under no throttle. Everything else was pretty normal as far as starting and power, such as it was, maybe mileage was down some. I think dumping fuel into the cylinders is a classic symptom for 'injector-pump-on-the-way-out'.

Let me just say, many thanks for your shared insight and thoughts. Just a few minutes here is worth untold busted knuckles and $$$. Everyone says get rid of the truck, but when it looks like it's falling apart before your eyes and carries you from Virginia to Montana twice without a single problem, how can you not love it?
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