1998 F150

john in la · May 19, 2013

A guy I use to work with was putting a 4.2 long block into a 1998 f150 and died before he could finish it. The truck has sat for a while about 1 year since motor was put in but never cranked over.
To make a long story short I was talking to his wife and asked if she wanted me to finish the job so her son would have a car. I had just done one on my dads truck a few years ago so knew a little about them.

Got it to my house and finished hooking all the wires and hoses up but it would not start. Found a no fuel problem and traced that to a bad fuel pump. Replaced it with on from a junk yard and motor fired right off.

I have only run it a few seconds and noticed another problem.
It has good oil pressure when raced up but drops to zero at idle per dash gauge.

So where can I hook a good mechanical gauge to test oil pressure???
If I find the same condition of good pressure when raced up but zero at idle what do you suggest I look at next.

Glen SW Wi · May 19, 2013

If all else fails, drop the pan and check the oil pickup tube. Had the same symptoms on our motorhome and they found that the pickup was not attached to the bearing bolt. The constant flopping up and down finally cracked the tube.
Good luck finding your problem.

ih_bug · May 19, 2013

I have had a few of the older ford engines do that and it was wore out rods and mains. replaced inserts and pump they were fine.

john in la · May 19, 2013

This is a completely rebuilt long block from a major rebuilder.
I would assume all the bearings are new and have been checked for tolerances.

john in la · May 19, 2013

While I really do not want to think about it I feel you are right glen.

The original motor threw a rod. I also called and asked his wife if she still had the recite for the motor he bought. Since I now know for sure he got a long block and not a complete motor I can assume it did not come with a pickup tube.

I am willing to bet he used the old pickup tube and it has a hair line crack from where the rod hit it.

Guess I will have to pull the motor back out and see what I can find.
Still would like to put a real gauge on it to be sure it has no pressure before I pull it.

This is a very clean truck. 3 door cab with 65000 original miles. It will make a very nice first truck for her son.

robgIN · May 19, 2013

take out the oil sending unit and put the guage in there, it could just be a bad sender. But it won't take long to find out with a manual guage hooked up.

hoof print · May 19, 2013

Did you see the old motor? Early 4.2's would bend rods after hydrolock, but I never remember them throwing them.

Probably is the sending unit, or maybe the wrong sending unit for your application.

36 Coupe · May 20, 2013

Ive called them a short block since we bought them rebuilt for 99 bucks.I was working with a fellow who was in a hurry.The oil pickup tube bolted to the block.No oil pressure on startup.He had the gasket sticking out with just one bolt through it.The oil gauge on my 96 f150 sticks on zero at startup at times and some times dosent drop to zero when the engine is shut off.

1998 F150

john in la

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Glen SW Wi

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ih_bug

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john in la

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john in la

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robgIN

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hoof print

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36 Coupe

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