88 idi low power at take off

[Guffey6]

Hey guys, I have a 1988 f250 idi non turbo zf5. 3 weeks ago I changed my injector pump with a used one off of a parts truck I bought (mine stopped pumping), and it ran so much better than it ever has. Last weekend I changed all fluids including rear diff and I changed out the valve cover gaskets ( looked very clean to my surprise)

So I decide to take it on a road trip( I travel for my job) a 300 mile round trip. The truck ran wonderfully the entire way down and 3/4 of the way back until... highway speeds it would almost act like I was running out of fuel every so often. Then, As i was stopped at a stop sign as I started to go it acted as if I were pulling a load starting out in 4th gear. (Not good). Very low power and sounded rough until it got up to around 40-45mph where it acted fine but with a lack of throttle. It barely made it up the mountain on which I live. Thankfully I got it home.

The whole time I'm thinking injector/ pump/ clutch slippage. I crack all injectors at idle and all 8 made the engine shutter. I also checked the schrader valve and my reading is 4psi with a tire gauge. Hopefully it's just a bad lift pump, considering I'm doing the facet pump mod soon, but if it's catastrophic I don't want to waste money.

Oil looks good
Coolant looks good
Plenty of fuel in tanks(fresh)
Been running power service in both tanks and in my filter
New wix fuel filter


Ps: while it's acting up under load, I'm getting greyish smoke. And It acts like I'm running out of fuel with the surge and stall.

Sorry if it's hard to read, I'm not a writer by no means. Please help!

 

[Guffey6]

Oh, and in neutral there's plenty of throttle response with no smoke.

What was stated above all happens only when in gear under load.

 

[Guffey6]

Any ideas?

 

[riotwarrior]

Not sure....does filtsr light come on?

May want try a new filter...couldnt hurt.

Search out tech 101 liqua molly diesel purge and watch and read...the thread...it may be something to try too.

 

[Thewespaul]

Verify that you have good fuel pressure and no leaks, if you are getting air in the lines it will cause similar symptoms. How did you time the pump when you installed it?

 

[Macrobb]

You've got a clog/issue in the fuel supply system, I'd check the tanks first and replace the cones of failure if they aren't perfect.
(last time I did it, I just pulled the bed. Easy to get to both tanks and fix them).

More than likely the fuel pump is just fine, and the facet won't help - you are either drawing a vacuum before the fuel pump, or getting air along with the fuel. Both will cause low power issues.

 

[Guffey6]

Not sure....does filtsr light come on?

May want try a new filter...couldnt hurt.

Search out tech 101 liqua molly diesel purge and watch and read...the thread...it may be something to try too.

No, no lights on the dash.

Verify that you have good fuel pressure and no leaks, if you are getting air in the lines it will cause similar symptoms. How did you time the pump when you installed it?

I have 4 psi at the schrader valve. Checked with a tire gauge. And I did not time it I just plugged and played, worked great for 3 weeks.

You've got a clog/issue in the fuel supply system, I'd check the tanks first and replace the cones of failure if they aren't perfect.
(last time I did it, I just pulled the bed. Easy to get to both tanks and fix them).

More than likely the fuel pump is just fine, and the facet won't help - you are either drawing a vacuum before the fuel pump, or getting air along with the fuel. Both will cause low power issues.

I will check all lines tomorrow evening, all these 4th festivities are piling up.


Thank you all for the responses.

 

[Guffey6]

I will add this, it may be a completely unrelated issue but on the way down my overtemp light came on. After realizing it was not over heating. Checked the sensor and it's shorted, so I unhooked it for the time being( can't find the part no.). My temp gauge sensor still works but, it kept climbing ( normally it sits around the N-O on normal) but it went all the way to M before it leveled out (2 hours of 70mph). And before all this started happening.

 

[Macrobb]

I will add this, it may be a completely unrelated issue but on the way down my overtemp light came on. After realizing it was not over heating. Checked the sensor and it's shorted, so I unhooked it for the time being( can't find the part no.). My temp gauge sensor still works but, it kept climbing ( normally it sits around the N-O on normal) but it went all the way to M before it leveled out (2 hours of 70mph). And before all this started happening.

If the extra temps happened along with the low power, it would make sense - less fuel pressure(under load) = retarded timing = hotter EGTs and more fuel burned = more heat in the cooling system.

Alternately, it could be either A, a failing thermostat(if you replace it, make sure to go with Motorcraft), or B, a grounding issue meaning that the reading is off(check your grounds between the block and the rest of the truck)

That being said... Pull out that overtemp sender and install a proper aftermarket gauge sender there.
Cheap digital gauges are around $20 off ebay, and you can even get one at your autoparts store for not much more.
I recommend something with an electrical sender vs the old "capillary tube" type, because they will end up reading low and be a real pain to install.

 

[Guffey6]

I am running a stant thermostat right now. I didn't know at the time to get a Motorcraft. I'm going to be replacing my water pump soon, so I will make all appropriate changes then.

I am headed to the shop now with clear lines to check for air intrusion, and to check the pump timing.

 

[Guffey6]

The pump was about 1/16 retarded from the existing mark. I moved it back to normal (both marks are lined up) and WHALLAH!! Thanks everyone for the help!! I can't express that enough!!!

Blows my mind at how it even ran before?!

No air intrusion so that's a plus!

 

[gnathv]

Did you time it with a meter or just match the marks? You will be amazed what proper timing does if it's only matched up to marks.

 

[Macrobb]

Or, if you don't have a meter... Just advance it a little at a time until it feels /worse/ than before, then back it off a little. Play with it and see how she feels - you'll get her really close to what you'd get with a meter with just a few adjustments.

And, as you've seen, there's quite a range that it will work in. You'll know if you went too far.

 

[Guffey6]

Gnathv, only with the marks. I don't have the equipment to do a full blown test.

Unless you have any tips or ideas?

 

[Guffey6]

Scratch that last post.. ok, I will play with it some more when I have time.

I've always had a little puff of white smoke at start up and now that is gone. But I have a little more black at WOT. I'm not a fan of that.