Early 6.9 low compression? continued...

[vaughnp]

Hello all, new to the forum, and my truck as well.

Its a 1989 f250 4wd that the previous owner swapped a 6.9 into. Not sure what happened to the 7.3.

Anyway, as I try to unravel the mystery and get it running, I came across this tag on the injection pump.

It says Remanufactured in red, and has a model of D2 and I think model number of S4822FD or PD its hard to make out from the picture.

I'm assuming its a DB2, looks like one from what I can tell. But the model number made me wonder...thoughts?

And yes, those are cobwebs...its coming along, hopefully someday she will even run! Working through all the great troubleshooting on this site, already replaced the shutoff solenoid, which no longer worked...have more parts on the way.

Thanks for a great forum. Sites like this make me happy that I took the plunge into this old diesel!

Vaughn

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[icanfixall]

Welcome to the forum. Our engines can only use the DB2 injection pump unless... you fabricate some new mounts for an inline. Do you know how many miles are on this pictured pump? My guess is way more than 125,000 miles. But... If it runs ok just use it till you get deeper into building up the fuel system. Please ask here before you purchase any fuel related parts. Way too many crap cheaters selling junk on ebay these days. the forum named... HALL OF SHAME has plenty listed. Its great reading too. How are you determining this engine is a swapped in 6.9??? You can clean off the drivers side of the block where the coolant sender and the injection pump is to read the serial numbers. A 6.9 will start with those numbers and the 7.3 starts with those numbers. This forum can even tell you what age this engine is.

 

[vaughnp]

From reading the forums I found that the cylinder head bolts on a 6.9 are 7/16 12pt, whereas the 7.3 is 1/2 12 pt. My engine has the 7/16 12pt head bolts.

Going to sneak out to the garage one last time tonight and see if i can find the serial...

 

[vaughnp]

Ok I think I found the number: 6_9DU2U044133* (the second character looked like maybe a 3 or 5 or a space, see pic?)

Also saw more orange RTV than I was hoping...not sure how bad a sign that is...also in picture.

edit:after some quick research, this looks like it may be the "thin wall" block?

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[bbjordan]

Welcome to the forum.

My research indicates:

DB2831-4822 04822 1813390C91 7.3 Liter 1990-92 Ford F Truck E Van (Alt.)

From the serial number it looks like an older weaker block:

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Not that's a really bad thing. When I got my 1986 F-250 it also had an old "weak" block, but it replaced a newer block that had failed. It's not unusual to find a 7.3 that has been replaced by a 6.9.
With proper maintenance and a few upgrades , there's no telling how far it will go.

 

[vaughnp]

Thanks for the info bbjordan!

Well, she's in pretty tough shape, but if I can get it running it would be great.

Have the return line components coming tomorrow as I suspect a leak. With that and all the info on this site I hope I'm headed in the right direction.

Things replaced so far are batteries, starter, and shutoff solenoid.

 

[IDIBRONCO]

The worst weak part of that block is the part right by the block heater. It has a tendency to crack there if you plug in the heater while the engine's cold. The way to use it is to plug it in when the engine's warm after running and you won't have the problem.

 

[Macrobb]

shutoff solenoid.

likely not an issue - I haven't seen these fail.

I'd bleed the lines first off - make sure the throttle is floored when cranking.

 

[vaughnp]

The old fuel shutoff solenoid wasn't clicking or making any noise even with 12 volts straight from the battery. New one clicks and appears to work as it should.

Maybe it was just stuck from sitting? Anyway easy one to rule out at least.

Tomorrow I will be bleeding the lines.

 

[vaughnp]

A friend and I tried bleeding the lines and were getting nothing no fuel at the lines.

Decided to check compression and I found the following numbers.

(Not sure how much it matters but this is an early block/engine (serial 044133) that's never been rebuilt to my knowledge.)

From what I was told it sat for the last 9-12 years.

Cranked with glow plugs out, using modified Harbor Freight compression tester as found on this website.

Cylinder PSI
1 140
2 165
3 200
4 180
5 200
6 180
7 180
8 160

I thought that seemed pretty low. So I added some oil through the glow plug holes and turned it over manually for a few minutes from the crank bolt just to be sure there would be no hydrolocking. I've experienced that in old 2 stroke motorcycles...

When I was sure the excess oil was ok cranked it over to clear the cylinders then did the test again.

Anyway, the following numbers came up:

Cylinder PSI
1 160
2 220
3 240
4 220
5 260
6 220
7 200
8 200

Is this even high enough to start the engine?

Not sure if this is just low from sitting, or because its from 1984 or so and just tired. Don't have good history of the engine unfortunately.

One interesting thing is that it also has a Turbo Engineering drivers side exhaust manifold, but its blocked off and doesn't appear to have ever had a turbo...I could be wrong though.

Was going to order a rebuilt IP and injectors this week, already ordered glow plugs.

With the intention of pulling the engine next summer and at least doing hone and re-ring...It won't see much use this winter, but would like to be able to move it in and out of the garage.

I researched and see way higher numbers reported by most folks. And that the early engine is lower compression but not sure how much lower the psi would be.

Any thoughts/advice greatly appreciated! Thanks for reading through this long post!

Vaughn

 

[Thewespaul]

It'll start but it may burn more oil than you may care to daily drive in

 

[vaughnp]

I wonder if the compression will go up much once things get flowing again? I suppose thats hard to say...but it would be nice to do the test on a warm engine.

And as far as oil consumption, that would be ok for awhile since it would only get used for occasional runs to the lumber yard etc.

 

[oregon96psd]

I wonder if the compression will go up much once things get flowing again? I suppose thats hard to say...but it would be nice to do the test on a warm engine.

Possible but not likely, once rings are stuck or loose their tension they are done. If it truely sat for 9-12 years its possible that condensation has them stuck in the grooves a little, but I probably wouldn't count on it. Leave the glow plug's disconnected and give it a dose of ether, see if it even has enough to hit off of that. At 160-240 psi it'll have a real hard time igniting diesel, that's getting close to gas engine number's lol.

Was it parked because it had no power and wouldn't start??

 

[Black dawg]

even once you get fuel to it, it will have a hard time even making smoke at the tailpipe with compression that low. Is it a manual trans? It will start if you can drag it around some, and the compression numbers might come up quite a bit after running some. The key with sticky rings (if that is what has happened) is to get the pistons HOT, to get the rings to let go. It can take quite awhile for the engine oil to clean up the ring grooves, and if it isn't used hard, the rings will continue to stick.

 

[Macrobb]

I'd be concerned about cranking speed as well. The huge ring gaps mean that you do lose some pressure through them, especially when cranking over slowly.

Also, make sure your gauge is working right. I had trouble with the HFT one myself, it not seating quite correctly and leaking a bit.. which will definitely give lower numbers.
Also, remember that you need to crank the engine over like 5-8 times(5-8 pulses on the gauge) to get an accurate reading, simply due to it filling up the gauge hose and such.