Diesel compression test? What are my options?

evy · 05-12-2014, 05:50 PM

Hi guys,

I'm looking to buy a E-series van and every time I find a good deal on a diesel model (6.0L or 7.3L) I can never find anyone near the seller's location to test the engines compression.

So I'm trying to find a solution to this problem, How about I test the engine myself?? here are 3 options, let me know what you think.

Keep in mind that I'm an amateur, I learn from watching and normally pretty quickly. I gotta admit I have a hard time understanding most of the replys I get here, I often have to google the abbreviations and expressions you engine gurus use, so don't go too hard on me

Option 1
Buy a basic compression test kit and do the standard test myself, how is the access to the glow plugs let's say for a 6.0L diesel?

Option 2
I saw this on Youtube, can I rent this equipment?
https://www.youtube.com/watch?featur...&v=kWvII9Vsdpw

Option 3?
The Ford dealer told me they can check the compression just by plugging the computer to the van, can I do the same thing with some sort of OBD II scanner?

Thanks again!

Pschitt · 05-12-2014, 11:06 PM

More important than compression test is to verify that all injectors are working properly. Could you bring the van to a dealer to plug the tester in ?

evy · 05-12-2014, 11:10 PM

Quote:

Originally Posted by Pschitt

More important than compression test is to verify that all injectors are working properly. Could you bring the van to a dealer to plug the tester in ?

All the Ford dealers I called this morning are booked solid till may 30th.
The van will probably be sold by then...

carringb · 05-12-2014, 11:20 PM

I don't recommend doing a traditional compression test on the 6.0 diesel. Very high probability (almost guaranteed) of breaking off a glow-plug connector which requires replacing the harness. Plus, just getting to all 8 would almost be easier just lifting the cab.

Instead, is a good scan tool to perform a "relative compression test" aka "cranking cylinder contribution test". This will show any weak cylinder. Of course, if they are all weak, this test won't show that. But you can also monitor torque output. If torque output is close to spec, and all cylinders are balanced during cranking, you can be pretty confident about the compression levels.

That said.... There's many other items I would inspect as well. A good 6.0 pre-sale inspection should be a minimum of 2-hours to perform all of the in-depth tests, to a visual inspection, and check the fluids. As mentioned, injectors are critical. If they were damaged by a bad FICM or oil filtration problem, you're looking at nearly $4,000 right off the bat if you have to pay somebody to do it. Also, fuel pressure under load, and EOT/ECT temps under load are critical checks that should not be skipped when looking at a 6.0.

evy · 05-12-2014, 11:29 PM

Quote:

Originally Posted by carringb

Instead, is a good scan tool to perform a "relative compression test" aka "cranking cylinder contribution test". This will show any weak cylinder. Of course, if they are all weak, this test won't show that. But you can also monitor torque output. If torque output is close to spec, and all cylinders are balanced during cranking, you can be pretty confident about the compression levels.

That said.... There's many other items I would inspect as well. A good 6.0 pre-sale inspection should be a minimum of 2-hours to perform all of the in-depth tests, to a visual inspection, and check the fluids. As mentioned, injectors are critical. If they were damaged by a bad FICM or oil filtration problem, you're looking at nearly $4,000 right off the bat if you have to pay somebody to do it. Also, fuel pressure under load, and EOT/ECT temps under load are critical checks that should not be skipped when looking at a 6.0.

Would this scantool help getting the information by any chance?
http://www.canadiantire.ca/en/pdp/ob...l#.U3GsXSgm-So

E350 · 05-13-2014, 12:11 AM

Hey carringb: Our 7.3 engines are not truly obdII compliant and don't have CAN bus, so the only real way to "scan" them is with AE. That's why earlier I suggested to evy that he ask on ford-trucks.com if there was anyone in Montreal with AE who would help him out.

Are your 6.0 engines obdII compliant? Do they have CAN?

Regardless, evy you are not going to be able to run a cylinder contribution test with anything but Auto Enginuity with the Ford software bundle except for the Ford diagnostic software which the dealership has.

Yes, there are some new apps like "Torque Pro" which are getting close to monitoring some sensors like AE does, but they are quirky and since they are nearly free, their software designers have not paid Ford to get the "inside" software secrets in the PCM to run the diagnostic tests that AE has paid Ford for and the Ford diagnostic software already has.

carringb · 05-13-2014, 12:27 AM

Quote:

Originally Posted by evy

Would this scantool help getting the information by any chance?
http://www.canadiantire.ca/en/pdp/ob...l#.U3GsXSgm-So

It looks like it can monitor the data streams, but it doesn't say how many. For some diagnostics, at least 3 live data streams is important. AutoEngenuity does 12, which as really nice when you have no idea what's going on (if anything).

carringb · 05-13-2014, 12:32 AM

Quote:

Originally Posted by E350

Hey carringb: Our 7.3 engines are not truly obdII compliant and don't have CAN bus, so the only real way to "scan" them is with AE. That's why earlier I suggested to evy that he ask on ford-trucks.com if there was anyone in Montreal with AE who would help him out.

Are your 6.0 engines obdII compliant? Do they have CAN?

Regardless, evy you are not going to be able to run a cylinder contribution test with anything but Auto Enginuity with the Ford software bundle except for the Ford diagnostic software which the dealership has.

Yes, there are some new apps like "Torque Pro" which are getting close to monitoring some sensors like AE does, but they are quirky and since they are nearly free, their software designers have not paid Ford to get the "inside" software secrets in the PCM to run the diagnostic tests that AE has paid Ford for and the Ford diagnostic software already has.

Yes, AE is my preferred DX tool. About the only thing better is a Ford VCM but the subscription is not cheap, so it doesn't make sense for family car. And you are right, AE does perform the functional test that most other tools don't. I have also used SnapOn Modus, which runs about $15,000 but for the 6.0 I found AE simply works better.

evy · 05-13-2014, 09:15 PM

Ok so no real compression test, instead I should have the Ford dealer verify the compression and injectors via the OBD port with theyr software?
Is that it?

carringb · 05-13-2014, 11:44 PM

Quote:

Originally Posted by evy

Ok so no real compression test, instead I should have the Ford dealer verify the compression and injectors via the OBD port with theyr software?
Is that it?

Yup. Also maybe ask them to check Turbo vane operation, injection pressure and duty cycle, FICM voltage, EOT/ECT and fuel pressure.

BTW - doesn't have to be Ford. Many independent shops have the software tools to perform the same test, usually at $50/hr less than a Ford dealer.

I would also recommend checking if it has a Motorcraft (or Raccor) oil filter, or maybe check prior service records. If aftermarket filters have been used instead, its at about the mileage that debris (from improper filter fitment allowing bypass) builds up enough that it ruptures the HPOP screen.