Ford 5000 diesel compression test

[Shawn C]

I have a 1973 5000 diesel which is hard to start, and I've finally had a little time to do a compression test. Here are the numbers I've found:

1. 260 dry, 360 wet
2. 260 dry, 360 wet
3. 225 dry, 400 wet
4. 195 dry, 300 wet

I know these aren't great, but I'm just looking for opinions. I've not adjusted the valves, but maybe that will help especially with cylinder 4.

I'm going to start by replacing the injectors, since I think the ones on the tractor are original. They are all really nasty and likely not spraying very well (I don't have a pop tester to verify), so hopefully that will improve things.

Are these compression numbers bad enough to justify a rebuild? Hopefully it will at least start better after I replace the injectors.

 

[Bern]

I have a 1973 5000 diesel which is hard to start, and I've finally had a little time to do a compression test. Here are the numbers I've found:

1. 260 dry, 360 wet
2. 260 dry, 360 wet
3. 225 dry, 400 wet
4. 195 dry, 300 wet

I know these aren't great, but I'm just looking for opinions. I've not adjusted the valves, but maybe that will help especially with cylinder 4.

I'm going to start by replacing the injectors, since I think the ones on the tractor are original. They are all really nasty and likely not spraying very well (I don't have a pop tester to verify), so hopefully that will improve things.

Are these compression numbers bad enough to justify a rebuild? Hopefully it will at least start better after I replace the injectors.

Assuming your compression gauge was accurate, and that you maintained an acceptable cranking speed throughout your test, those numbers are dismally low. Your wet readings are meaningless IMHO because all you did was fill the piston bowl with oil, which increased your static compression ratio.

Unless you have valves that are too tight (i.e. not closing), adjusting them isn't going to change anything. You either have a very tired engine and/or an inaccurate compression gauge. You might do well to find another one to confirm your readings. Also, the fact that the numbers dropped from 1-4 makes me think your battery might have petered out there at the end.

 

[Shawn C]

Assuming your compression gauge was accurate, and that you maintained an acceptable cranking speed throughout your test, those numbers are dismally low. Your wet readings are meaningless IMHO because all you did was fill the piston bowl with oil, which increased your static compression ratio.

Unless you have valves that are too tight (i.e. not closing), adjusting them isn't going to change anything. You either have a very tired engine and/or an inaccurate compression gauge. You might do well to find another one to confirm your readings. Also, the fact that the numbers dropped from 1-4 makes me think your battery might have petered out there at the end.

Thanks for the insights. Battery is less than a year old and was in fact on a charger for several hours before and during the testing, and I have a new starter installed a few months ago. Cranking speed was good and consistent, and I cranked for several seconds on each test until the gauge stabilized. The compression tester is for diesel engines, and it's in good shape, so I don't think there are any issues there. I have another gauge set I will try though tomorrow just in case.

Also, I didn't test in firing order, but rather 3, 4, 2, 1 (no particular reason). I mainly added some oil for the wet test to try and rule out a valve issue. I re-tested cylinder 4 a couple of times, just to verify, and those are the best readings I could manage.

Engine is probably tired. This tractor sat for several years and was likely not maintained very well before that. I didn't pay much for it, since I assumed it would need work. It actually runs pretty well, but it's hard starting.

I didn't see any leak down, at least not quickly (I didn't do a full leak-down test). Cylinders each held pressure after each compression test.

 

[Bern]

Thanks for the insights. Battery is less than a year old and was in fact on a charger for several hours before and during the testing, and I have a new starter installed a few months ago. Cranking speed was good and consistent, and I cranked for several seconds on each test until the gauge stabilized. The compression tester is for diesel engines, and it's in good shape, so I don't think there are any issues there. I have another gauge set I will try though tomorrow just in case.

Also, I didn't test in firing order, but rather 3, 4, 2, 1 (no particular reason). I mainly added some oil for the wet test to try and rule out a valve issue. I re-tested cylinder 4 a couple of times, just to verify, and those are the best readings I could manage.

Engine is probably tired. This tractor sat for several years and was likely not maintained very well before that. I didn't pay much for it, since I assumed it would need work. It actually runs pretty well, but it's hard starting.

I didn't see any leak down, at least not quickly (I didn't do a full leak-down test). Cylinders each held pressure after each compression test.

Compression testers have a built-in check valve that holds the pressure after each successive compression stroke. This is why it appeared that the cylinders were holding pressure, when in fact it was the gauge doing that.

 

[Shawn C]

Compression testers have a built-in check valve that holds the pressure after each successive compression stroke. This is why it appeared that the cylinders were holding pressure, when in fact it was the gauge doing that.

Ah, yeah I forgot about that. I'll double-check that my seal around the compression test adapter is good then.

 

[Destroked 450]

Compression is certainly low, is there a place you can take the injectors to have them pop tested, they likely need rebuilt but I like to test them first before spending money
Have you checked the oil level in the injection pump
Have you tried starting it with the fuel enrichment button pushed in
We have a early model 5000 that is getting pretty tired, it doesn’t start well first time unless the fuel enrichment button is pushed in, yes that’s a band aid way of starting a worn engine but that tractor isn’t used much and we’ve got by a number of years without having to do a engine rebuild

 

[Shawn C]

Compression is certainly low, is there a place you can take the injectors to have them pop tested, they likely need rebuilt but I like to test them first before spending money
Have you checked the oil level in the injection pump
Have you tried starting it with the fuel enrichment button pushed in
We have a early model 5000 that is getting pretty tired, it doesn’t start well first time unless the fuel enrichment button is pushed in, yes that’s a band aid way of starting a worn engine but that tractor isn’t used much and we’ve got by a number of years without having to do a engine rebuild

This one has a CAV pump, so no oil in the pump as far as I know. I do always hold the glow plug button in for 30 seconds or so before trying to start it. I might go ahead and buy one of the chinese pop testers, since they seem to work ok for light duty use.

On another note, last night when I did my first test was a little bit of a rush job (getting late and dark, storm rolling in), so I used one of the original fiber washers around my compression adapter. This adapter doesn't fit as tight as the injectors, so I think I was leaking a little pressure.

I was able to redo everything this morning, using a much better seal, and my results are better now:

1. 280 dry
2. 280 dry
3. 280 dry
4. 240 dry

Do these numbers justify a rebuild? I'm going to get new injectors in first (actually rebuilding with new nozzles), so hopefully that will help at least in the short term.

 

[Bern]

This one has a CAV pump, so no oil in the pump as far as I know. I do always hold the glow plug button in for 30 seconds or so before trying to start it. I might go ahead and buy one of the chinese pop testers, since they seem to work ok for light duty use.

On another note, last night when I did my first test was a little bit of a rush job (getting late and dark, storm rolling in), so I used one of the original fiber washers around my compression adapter. This adapter doesn't fit as tight as the injectors, so I think I was leaking a little pressure.

I was able to redo everything this morning, using a much better seal, and my results are better now:

1. 280 dry
2. 280 dry
3. 280 dry
4. 240 dry

Do these numbers justify a rebuild? I'm going to get new injectors in first (actually rebuilding with new nozzles), so hopefully that will help at least in the short term.

Going off memory, Ford spec is 275 PSI minimum, so you're right on the borderline. I believe that 350-375 is considered "good".

 

[Shawn C]

Thanks, I appreciate that. Minimum is fine for now, since I know I have other work to do anyway. The PTO was running full time when I got it, and I was able to fix that by adjusting the PTO brake, but now the PTO doesn't turn at all. The shaft had been broken and welded at some point in the past, so I wanted to replace the PTO shaft anyway. I'll start a separate thread on that when I get time to work on it.

 

[Shawn C]

I got my new pop tester set up and was able to test the old injectors. Not surprisingly, they all just squirted like squirt guns at relatively low pressure (no definite pop pressure, but they would start releasing around 2000 psi) and with no visible atomization. I have my new nozzles, but I've not had time yet to do anything with them. I'll try to get the injectors rebuilt some time this week and will try the pop test again.

Can someone confirm the pressure these should pop? I've read 2750 psi, but just wanting to verify.

 

[Shawn C]

Just to update, I rebuilt and reinstalled the injectors and the tractor starts easily now.