BlueKitsune

Hi, I'm new to the forum and looking for help. I have recently become the owner of a 1987 F-series F150 4x4 with an Inline 6 300 EFI motor coupled to a NP435 with a divorced transfer case. I bought it from the estate of a farmer who took relatively good care of it judging by the receipts and paper work left in the glove box.

Ok, introductions aside, down to the symptoms.

First problem, the thermal clutch on the radiator fan gave out on a hot summer day. Didn't find out about it till the truck died on me and wouldn't restart till the engine cooled back off. No warning light and the gauge never left the low end of normal. Replaced the thermal clutch ran fine for a while.

Second problem, under power the truck will randomly loose power, drop in RPM, shudder and shake, and finally die. What gear it's in, whether or not the tranny is engaged to the engine, pitch of the road, long story short the problem seems to occur regardless of noticeable external factors.

Third problem, recently the shifter has begun violently shaking even while in gear. For this I'm looking at changing the gear oil to see if it makes a difference.

Forth problem, when I ease off the gas to get better gas mileage but maintain my speed and then increase it to get more power to get up a hill the engine hesitates big time and tries to die.

So, what I've replaced and done/experiences. I've run codes of the OBD I system and only got an EGR valve problem turns out it was stuck and needed to be cleaned no prob, replaced. Second problem persists and generates no codes. I thought it was about time to replace the spark plugs and the wires. Went with OEM Motorcraft copper plugs and Chilton recommended wires. All plugs were tan colored and showed evidence of use. Second problem persists continues to generate no codes. After several episodes of the problem and continued attempts to diagnose it I got fed up and took it to a trust worthy mechanic who had it for six months trying to diagnose it as well, needless to say it stumped him. Since then in the three months I've had it it's pulled the random fail twice in rapid succession both times at speed. And both times it started back up when I popped the clutch.

This truck has me at wits end but I'm not ready to give up on it. I don't know if it's one problem manifesting through several symptoms or several problems that just happen to be popping up in short order. Ether way I need help and I hope that your experiences and suggestions help better than my research. Thanks.

Chris_1

iTrader: (1)

Is it EFI ? What's the fuel pressure at ?
EFI v8's run at 30 to 45 psi, but early 6's like yours (assuming yours is EFI) were designed to run at 45 to 60 psi.
That might be a possibility.

nayrb64

I agree with Chris - as it sounds like possible fuel. I would check the pressure and if it's low, change all fuel filters and recheck the pressure. I changed fuel filter on my 95 4.9L and fixed the low pressure problem. Filters are cheap

BlueKitsune

It is an EFI I6 300, and I tested the fuel pressure today, holds steady at 50 psi @ KOEF, 52 psi @ KOEO, and under load dips to 45 psi.

In other news, took it in to get the gas gauge checked and found out that both tanks had a layer of bad gas on the bottom of the tank along with some sludge. When I say bad the gas had degraded to the point it smelled like turpentine.

I also pulled the spark plugs to check if they were firing alright and think I found the problem. Cylinder #1's spark plug is fouled with oil. Thinking that was odd I ran a compression test. Front to back: 0, 100, 102, 99, 100, 98. That 0 is a big problem, it seems that I have 1 of 3 problems, a) blown piston rings, b) blown head gasket, or c) the nightmare inducing cracked head.
Ether way I'm probably looking at a new engine. Any suggestions on where to get a replacement OBDI I6 300?

Chris_1

iTrader: (1)

Could also be a valve. Do a wet test on #1.
Also 45 psi under load is the very bottom end of being enough pressure to keep that engine running.
So looks like 2 issues.

SpeedThrills

Could be a stuck valve, but it would probably, but not necessarily have a tapping rocker/pushrod to go along with it. You didn't mention any tapping. Old gas can make a valve stick.
Could be a burned valve, leaking the compression.
With 0 compression in one cylinder, you should have noticed a consistent dead miss, in rhythm.
Don't know exactly what you mean by "blown rings", they generally wear out, and the other cylinders would've too. They could break, I suppose, but broken or worn, it would burn oil and blow blue smoke. You didn't mention that.
A bit premature to be looking for a replacement engine, until you troubleshoot and determine what's wrong.

Edit: Chris, do you think a wet test will improve 0? I suppose it can't hurt.

Chris_1

iTrader: (1)

No, I don't think it will improve it but it should be done anyway just to say I did that and got x result. As you said it can't hurt.
Actually I don't think it would be rings - even a piston by itself would probably make some compression. The rings would have to be completely gone to get 0 compression and even then it might bump the needle. And as you said, the truck would be trailing blue smoke like a cropduster.
I'm also thinking that a bad head gasket or cracked head would still show something on the compression tester - not that it could hold any pressure, but I think you'd see something happen when that 4" coffee can slides up the tube. Maybe not much, but probably something.
I'm picturing a valve bent over or otherwise jammed wide open - that's the most likely possibility to get a 0 reading I think.
The good news is that if it's 1 bad valve, that's repairable without breaking the bank.
The rest of the cylinders don't have high compression but it's nice and even, I'll bet having the valves and seats ground while the head is off would bump those numbers up a bit.

BlueKitsune

This is my first my first experience with an I6 300 and it hasn't changed it's sound since it came into my possession, I'd heard that the i6's had an interesting sound so never crossed my mind that it was missing a cylinder. But once I was told what to listen for it was obvious.

As for the smoke, there's been none so it's not burning oil. And near as I can tell the cylinder isn't firing. When I tested the spark plug, it sparked properly so it's not an electrical issue.

Put a little oil in the cylinder and did a wet test, the highest it spiked to was 10 psi over the course of 5 compression cycles. Each test the pressure bled off in under a minute.

So, I've never had an engine rehabbed what should I be looking at and who should I be looking at so I don't get held over a barrel for a ridiculous price.
I know how to swap an engine, but this is new.

Summers22

iTrader: (2)

I know you said pressures are good, but my 92 I6 did this and it was the fuel filter. Same symptoms as you said in your first post " under power the truck will randomly loose power, drop in RPM, shudder and shake, and finally die. What gear it's in, whether or not the tranny is engaged to the engine, pitch of the road, long story short the problem seems to occur regardless of noticeable external factors".

LoboMike

Have you pulled the valve cover to see the rocker arm movement? My suspicion is a valve issue & possibly a swallowed valve, lifter issue, push rod issue, or similar. Pulling the valve cover is easier than pulling the head (if you haven't already.

HTH,
Lobo