Can you put split shot injectors in a OBS engine?

Bustedknuckles · Nov 28, 2014

I have a 2001 super duty here I just put a 94 short block in. I switched everything including the front cover and pickup tube over and now the truck has a rough idle and miss while driving. Contribution and buzz test come back good but I suspect injectors anyway as it had coolant in the oil but it ran Ok when it was dropped off so the customer is having a hard time believing that and I don't blame him. The customer talked to XDP a couple days ago and they told him it is caused by running split shot injectors in a engine designed for single shot. I have a hard time believing it as I thought guys did OBS short block swaps all the time? Any help would be appreciated!

superpsd · Nov 28, 2014

As far as I have read split shots have been swapped into obs trucks before with the proper tuning to run them. I think a 7.3 is a 7.3. Guys have also swapped the obs motors into the PMR years as well to get a stronger bottom end. Think your problem is somewhere else?

mandkole · Nov 28, 2014

The long block doesnt care what injectors go into it and vice versa. I gather you swapped wiring harnesses too? Since you changed the pickup tube, have you checked for steady oil pressure/supply? Any oil aeration? I'd be checking my work again--just when you think everything is covered.. ugh.

Bustedknuckles · Nov 28, 2014

mandkole said:
The long block doesnt care what injectors go into it and vice versa. I gather you swapped wiring harnesses too? Since you changed the pickup tube, have you checked for steady oil pressure/supply? Any oil aeration? I'd be checking my work again--just when you think everything is covered.. ugh.

Thats exactly what I thought! Are the pistons identical? Yes i did, i used nothing but the rotating assembly and heads. How do you check for oil areation?

lincolnlocker · Nov 28, 2014

Bustedknuckles said:
Thats exactly what I thought! Are the pistons identical? Yes i did, i used nothing but the rotating assembly and heads. How do you check for oil areation?

yes the longblock is identical. just a couple cosmetic revisions when going to a sd block.. check for aeration, with the truck running pull the dipstick and it will be covered in bubbles(more foamy i guess) or as soon as you **** it down pull the dilstick.... there will always be a couole bubbles but it shouldn't ever look like dish foamy dishwatter if you will...

live life full throttle

mandkole · Nov 28, 2014

Yeah, this should be a straight forward swap and it looks like you have everything covered. Just hoping you dont have an oil pickup or supply issue. Did you check the health of the 94 motor (compression and leakdown)? If you are somehow pulling air thru the pickup tube, the oil will be foamy in the reservoir and in the pan.

gnxtc2 · Nov 28, 2014

The only difference is the SD cam doesn't have the eccentric to run the mechanical fuel pump that is in the OBS motor.

My concern would be why coolant was in the oil.

Billy T.
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Bustedknuckles · Nov 28, 2014

mandkole said:
Yeah, this should be a straight forward swap and it looks like you have everything covered. Just hoping you dont have an oil pickup or supply issue. Did you check the health of the 94 motor (compression and leakdown)? If you are somehow pulling air thru the pickup tube, the oil will be foamy in the reservoir and in the pan.

No I didnt. It does have a decent amount of blowby but it cranks smooth with fuel disabled so I dont think it has any dead cylinders. I drained the oil right after running it and it wasnt foamy at all. Also I didnt remove the pickup tube from the front cover at all so im thinking thats not my issue. I just wish XDP wouldn't have told this guy that he needs to run his single shot injectors.

lincolnlocker · Nov 28, 2014

Bustedknuckles said:
No I didnt. It does have a decent amount of blowby but it cranks smooth with fuel disabled so I dont think it has any dead cylinders. I drained the oil right after running it and it wasnt foamy at all. Also I didnt remove the pickup tube from the front cover at all so im thinking thats not my issue. I just wish XDP wouldn't have told this guy that he needs to run his single shot injectors.

with the fuel cut off it will crank super smooth, even pass a cct but all that means is that all the cylinders are equally good or equally bad and could have bad compression on all eight...

live life full throttle

Bustedknuckles · Nov 28, 2014

lincolnlocker said:
with the fuel cut off it will crank super smooth, even pass a cct but all that means is that all the cylinders are equally good or equally bad and could have bad compression on all eight...

live life full throttle

Good point. I guess if the injectors check ok I will do a compression test.

lincolnlocker · Nov 28, 2014

Bustedknuckles said:
Good point. I guess if the injectors check ok I will do a compression test.

good idea

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Arisley · Nov 28, 2014

Double check UVCH's.

lincolnlocker · Nov 28, 2014

Arisley said:
Double check UVCH's.

what he said^^^^^^^^ again....

live life full throttle

Bustedknuckles · Nov 28, 2014

Arisley said:
Double check UVCH's.

Just did resistance checks. All good, coming apart now for a compression check and then taking the injectors to get tested. This thing has me really frustrated!

Bustedknuckles · Dec 1, 2014

Bustedknuckles said:
Just did resistance checks. All good, coming apart now for a compression check and then taking the injectors to get tested. This thing has me really frustrated!

Best of 390 and worst of 320. Obviously that's bad, but is that bad enough to cause a rough idle and "miss"?

ghohouston · Dec 1, 2014

Bustedknuckles said:
Best of 390 and worst of 320. Obviously that's bad, but is that bad enough to cause a rough idle and "miss"?

I doubt it, it could cause some inconsistencies idling, but I don't think it would cause an all out miss.

lincolnlocker · Dec 1, 2014

Bustedknuckles said:
Best of 390 and worst of 320. Obviously that's bad, but is that bad enough to cause a rough idle and "miss"?

hot or cold when tested?

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Bustedknuckles · Dec 1, 2014

lincolnlocker said:
hot or cold when tested?

live life full throttle

Cold.

lincolnlocker · Dec 1, 2014

lincolnlocker said:
hot or cold when tested?

live life full throttle

thats not horrible... before i had whitey rebuilt, it was just over 300 across the board.... hot... it ran fine. just a lil extra smoke on a cold start.

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Bustedknuckles · Dec 3, 2014

So I got the results back from getting the injectors tested. Three are flowing no fuel at idle and the rest are only flowing 2 or 3 cc's when it should be 20. I'd say I found the problem! Lol