7.3 injector refresher please

dieseldoc · December 20, 2008

Vehicle in question is a 96 F-250 7.3 and 5 spd 160,000mi. All scan tool test come out ok. When wathching PIDs I found the IPR% to be 11(a bit higher than I am used to seeing)

Customer brought it to me for hard starting, fuel leak and exhaust smell in the cab. I found a lot of fuel in the lifter valley, up pipes and down pipe clamp leaking. Resealed the up pipes and repaired the clamp leak. Removed the filter base to reseal and install new hoses. The interesting part is that there is a black film on everything in the fuel system. Pulled a sample out of the tank and the fuel in the tanks is a little dark. I found bits of rubber in the regulator. Now obviously the injector seals are breaking apart and going into the regulator, and High pressure oil is getting into the fuel system. In your guys experiences at this mileage would you remove the injectors and reseal, or replace the injectors? I installed the filter base and ran the truck to remove all the air from the system and started cold and found that it cranks longer than it should with a lot of white smoke(glow plug system is working correctly, starting system working as it should and cranking speed ok). In my experiences with an IPR% at 11 and above and the white smoke leads me to think the injectors are getting worn and ready for replacement. Will drain the filter base and fill with stanadyne to see if it improves tomorrow. Dont want to reseal injectors to find they are shot and need to be replaced. Thanks for you opinions guys.

Fredsvt · December 20, 2008

It sounds like you have a couple of issues, failing o-rings leading to the lube oil in the fuel. Your IPR will be higher with leaking o-rings.

The second issue is the white smoke while cranking.

That means there's not enough heat to light off the fuel, if the glow plugs pull about 195 amps and it still does it. I'd be checking base engine compression (low compression will make it crank fast) and check blowby.

The other issue is one I've only seen once, a failing injector(s) that are staying stuck open when cold.

Usually though, bad older injectors fail to deliver fuel when cold.

You can hear the injectors click (ICP builds quick) while cranking, using a remote starter button, standing near the motor with the hood up, but no smoke as they don't deliver anything. Been there with trucks that idle way too much and don't see enough oil changes.

Bruce Amacker · December 20, 2008

Vehicle in question is a 96 F-250 7.3 and 5 spd 160,000mi. All scan tool test come out ok. When watching PIDs I found the IPR% to be 11(a bit higher than I am used to seeing)

9-11% is normal on the 7.3.

Customer brought it to me for hard starting, fuel leak and exhaust smell in the cab. I found a lot of fuel in the lifter valley,

LPFP leaking? Fuel heater terminal leaking? Both are very common.

up pipes and down pipe clamp leaking. Resealed the up pipes and repaired the clamp leak. Removed the filter base to reseal and install new hoses. The interesting part is that there is a black film on everything in the fuel system. Pulled a sample out of the tank and the fuel in the tanks is a little dark. I found bits of rubber in the regulator. Now obviously the injector seals are breaking apart and going into the regulator, and High pressure oil is getting into the fuel system. In your guys experiences at this mileage would you remove the injectors and reseal, or replace the injectors?

It's a crapshoot. If it were mine, I'd hang injectors.

I installed the filter base and ran the truck to remove all the air from the system and started cold and found that it cranks longer than it should with a lot of white smoke(glow plug system is working correctly,

Check glow plug AMPERAGE with an amp clamp at the GP relay to verify this- it should be 190ish at initial key-on, dropping to about 125ish after 30 seconds.

White smoke cranking means it is getting fuel delivery but not combustion. This is most commonly from low GP amperage, low cranking speed, or worn injector tips that are not atomizing the fuel properly. You're definitely on the right track.

starting system working as it should and cranking speed OK)

Cranking speed should be at least 150rpm cold and about 175rpm hot.

Double check it with a scan tool, as your ears will deceive you!

. In my experiences with an IPR% at 11 and above and the white smoke leads me to think the injectors are getting worn and ready for replacement.

Yes, likely.

Will drain the filter base and fill with stanadyne to see if it improves tomorrow.

Good move.

Don't want to reseal injectors to find they are shot and need to be replaced. Thanks for you opinions guys.

Look at the MFDES (Mass Fuel Desired) PID, as it will tell you if the engine is starving for fuel from low pressure or weak injectors. I like to see 8-10mg idling. If it's 14-16mg idling, it's starving for fuel and the injectors are likely bad. (You did check fuel pressure under load, RIGHT?)

Good Luck!

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dieseldoc · December 20, 2008

I checked the glow plug amperage when checking the glow plug system, was ok at 188. Cranking speed with the scan tool hooked was 149 to 153 cold. Fuel pressure under load was ok. I replaced the lpfp about 4 months ago for this customer, I replaced the glow plugs and relay (two plugs burnt out and contacts were burnt in the relay) at that point as well. The customer wanted a compression test done when I replaced the glow plugs. Compression was 340-360. Will watch the MFDes to see what it is and see how it does with the stanadyne in the filter base this afternoon. I think I am going to reccomend injector replacement. This one is acting exactly like a 94 I had a year ago. Put a new set of alliant injectors in and the customer said the truck never started or ran that well when it was new. Thanks for the input guys, I just want to do the right thing for my customers. I would hate to waste there money or my time.

Bruce Amacker · December 20, 2008

I checked the glow plug amperage when checking the glow plug system, was ok at 188. Cranking speed with the scan tool hooked was 149 to 153 cold. Fuel pressure under load was ok. I replaced the lpfp about 4 months ago for this customer, I replaced the glow plugs and relay (two plugs burnt out and contacts were burnt in the relay) at that point as well. The customer wanted a compression test done when I replaced the glow plugs. Compression was 340-360. Will watch the MFDes to see what it is and see how it does with the stanadyne in the filter base this afternoon. I think I am going to recommend injector replacement. This one is acting exactly like a 94 I had a year ago. Put a new set of alliant injectors in and the customer said the truck never started or ran that well when it was new. Thanks for the input guys, I just want to do the right thing for my customers. I would hate to waste there money or my time.

Great work, but the compression is a bit low at 340-360. (What's your altitude?) A good cylinder is 400+, anything under 350 is suspect at sea level. Warn the cust about engine wear and hang some injectors. Does the intake hose/turbo/air cleaner show signs of dirt intrusion? Does it have the updated air cleaner lid and steel bolts?

Good Luck!

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dieseldoc · December 20, 2008

The altitude here is about 900 ft I think. Unfortunately it does not have the updated air cleaner cover, However there arent signs of dirt in the air piping and the compressor wheel looks good. I have suggested the air cleaner update to her twice but, she wont go for it. Maybe with these compression numbers as some proof it will convince the customer. The standadyne helped. I will give an estimate for new injectors and go from there. Thanks a bunch for the advice guys.