[Nplsdvr]

I bought a new compression tester and read the instructions. It seems pretty straight-forward and makes sense, but the instructions didn't say anything about fuel - do I need to pull the fuel pump fuse? trip the intertia switch? Or just leave it alone?

Thanks for your input!

Nic in B'ham

 

[pextor]

you don't have to mess with the fuel system at all.

 

[EscorGo]

I never have. You aren't going to crank on it that much.

 

[Nplsdvr]

really??!! So, will it just dump fuel while I'm cranking? Granted, the plugs will be out, so it will probably just evaporate, but it just sounds so counterintuitive.

 

[pextor]

pretty much.

 

[EscorGo]

If it will make you feel better, I think there is a fuse you can pull for the injectors.

 

[FordMan59]

I think most manuals say to disable the fuel system. but I usually don't.

 

[pextor]

but I usually don't.

same here.

 

[Nplsdvr]

o.k. so basically:

1. warm up the engine to operating temp
2. pull all the spark plugs
3. take the coil lead off the distributor and ground it to the block
4. fully open the throttle body (or just floor the accelerator pedal)
5. put the tester in the cylinder
6. crank the key for 4 to 10 cycles until a consistent reading is reached
7. repeat steps 5 & 6 for all cylinders
8. put all the spark plugs back in and put the coil lead back on the distributor.

Dats it fo' dat, right?

 

[88scortgt]

o.k. so basically:

1. warm up the engine to operating temp
2. pull all the spark plugs
3. take the coil lead off the distributor and ground it to the block
4. fully open the throttle body (or just floor the accelerator pedal)
5. put the tester in the cylinder
6. crank the key for 4 to 10 cycles until a consistent reading is reached
7. repeat steps 5 & 6 for all cylinders
8. put all the spark plugs back in and put the coil lead back on the distributor.

Dats it fo' dat, right?

9. if the pressure is reading low, put a small amount of oil in the cylinder an re-test.
This will tell you if the low reading was due to bad rings.

 

[g4ebguy]

.. - remove all spark plugs....disconnect fuel somehow... i just pull the injector harness's off....the reason for this cuz u dont wanna spray fuel in there when ur doing test can throw it off....also disconnect ignition i just unplug the coil harness...and i hook up a battery charger to the battery also full throttle the pedal.and i then crank the engine till i hear the 7th room maroom maroom then i get out and look at the gauge... if any of the readings are abnormally low....retest if still low but a dab of oil in the cyl.... if the reading goes up maybe bad rings....also i do mine when the engine is cold... because i hear u can strip the threads easier on a heated engine.
But i have gotten off readings cold...one time my hyundai said it had 65 psi on 1 cyl and then i tested it later and it was 185.

 

[celery952]

I dunno if its all 91+ escorts or maybe mine had this implemented by 95


at least on all obd2 fords (mine was obd1 so I really dont know what year this was implemented)

but if you hold the gas pedal WOT when cranking it disables the fuel injectors specifically for this purpose


and really to get the closest to true readings you should have the throttle wide open anyway

 

[madmatt2024]

o.k. so basically:

1. warm up the engine to operating temp
2. pull all the spark plugs
3. take the coil lead off the distributor and ground it to the block
4. fully open the throttle body (or just floor the accelerator pedal)
5. put the tester in the cylinder
6. crank the key for 4 to 10 cycles until a consistent reading is reached
7. repeat steps 5 & 6 for all cylinders
8. put all the spark plugs back in and put the coil lead back on the distributor.

Dats it fo' dat, right?

I thought it was bad to remove spark plugs from a hot aluminum head.

 

[celery952]

I think its supposed to be cold, but you get better compression readings when its warm, and effectively you need to know what it is when its warm, cause its warm when its running.... meh we change plugs on peoples vehicles who are waiting all the time......your not supposed to do it but noone ever has any issues