[bryanmk3]

So my car sat for a few months while waiting on parts for a manual swap and in the meanwhile the starter went out and couldnt start the car and finally got it done and now theres low compression on the first two cylinders (others havent been tested) and the car started up just fine before it sat, and i dont know why its doing that. Does anyone know what it could be?

 

[omicca]

Try putting a cap ful of oil in those cylinders through the spark plug holes and testing again

 

[bryanmk3]

im gonna go check the car out tomorrow and try that

 

[Strokercharged95GT]

Test all 6 and post the numbers.

 

[3p141592654]

Did you have the throttle open during the compression test?

 

[bryanmk3]

Did you have the throttle open during the compression test?

i didnt do the test the mechanic doing my swap did, is it supposed to be opened or not? i will be doing on tomorrow

 

[3p141592654]

wide open. But let' see the numbers for all 6

 

[IdahoDoug]

There's no logical reason for that to happen. Did you test compression before parking it, so you KNOW it was good before? Does your mechanic have a boat payment to make, so now he's "discovered" you need a rebuild in addition to the cash flow he enjoyed from the swap?

 

[bryanmk3]

There's no logical reason for that to happen. Did you test compression before parking it, so you KNOW it was good before? Does your mechanic have a boat payment to make, so now he's "discovered" you need a rebuild in addition to the cash flow he enjoyed from the swap?

didnt test before hand but the car started right up, now it wont start

 

[IdahoDoug]

Wow this gets worse. So the engine won't start and the mechanic has "discovered" low compression and blames it for not starting? I call BS. He's done something wrong in the swap and knows that a full engine teardown will look nice in his bank account, plus he's likely to figure out what he did wrong while being paid for a massive new job.

 

[Strokercharged95GT]

If you have all the spark plugs out, doing all 6 holes should take 4-7 mins max.

What i suspect the mechanic did was remove only the first two plugs, collect compression numbers on 1 and 2 only. The added compression from not removing the plugs from 3 through 6 would make the starter turn slower and skew compression lower. I have never heard of only being provided 33% of the results on a test. Its good to have the other 4 readings to see what the balance is and high/low. This is all conjecture and heresay so you can ignore my theory, but it makes sense.

 

[Wreckless]

I've also seen "professional" mechanics use a faulty compression tester.

Does this mechanic have any kind of good reputation for working on Supras or other older Japanese cars?

 

[Asterix]

Consider that you have to pull half the intake apart to get to spark plugs 3 and 4. A proper compression test on all 6 cylinders has the throttle body sitting on the floor next to the car. I would not believe any test done otherwise.

 

[bryanmk3]

Wow this gets worse. So the engine won't start and the mechanic has "discovered" low compression and blames it for not starting? I call BS. He's done something wrong in the swap and knows that a full engine teardown will look nice in his bank account, plus he's likely to figure out what he did wrong while being paid for a massive new job.

could be that but also what would a trans swap do to the engine is what has me stumped

 

[bryanmk3]

I've also seen "professional" mechanics use a faulty compression tester.

Does this mechanic have any kind of good reputation for working on Supras or other older Japanese cars?

yea he's known for doing these manual swaps in my area

 

[bryanmk3]

Consider that you have to pull half the intake apart to get to spark plugs 3 and 4. A proper compression test on all 6 cylinders has the throttle body sitting on the floor next to the car. I would not believe any test done otherwise.

yea im gonna have to test it later today or tomorrow because of finals but ill make sure to test it right

 

[IdahoDoug]

You asked above "What would a trans swap do to the engine". Well, depends on how he did the swap. If he left the engine in and just pulled the trans and switched them - not much. But if he pulled the engine - a LOT could go wrong. Forgotten grounds, rough treatment of a 35 year old wiring harness, changed the engine computer to a manual model and didn't connect things right, etc, etc. You are wise to check the compression yourself as I have a suspicion the mechanic knows with all that going on he knows he overlooked something. And as stated, he knows the best strategy is to say "That naughty car broke itself while I was working on it. But I'd be happy to charge you to see what it did to itself".

What I'd also like to hear is how do you have a nonrunning car back from a shop? You gave him a running engine'd car for a tranny swap. He gave you back a nonrunning car with a different tranny and you said, what? - that's OK, I'll pay you and take the car home? So how did his test drive go to verify the tranny is fully functioning in all gears and at all speeds, etc.......cough......?

 

[bryanmk3]

You asked above "What would a trans swap do to the engine". Well, depends on how he did the swap. If he left the engine in and just pulled the trans and switched them - not much. But if he pulled the engine - a LOT could go wrong. Forgotten grounds, rough treatment of a 35 year old wiring harness, changed the engine computer to a manual model and didn't connect things right, etc, etc. You are wise to check the compression yourself as I have a suspicion the mechanic knows with all that going on he knows he overlooked something. And as stated, he knows the best strategy is to say "That naughty car broke itself while I was working on it. But I'd be happy to charge you to see what it did to itself".

What I'd also like to hear is how do you have a nonrunning car back from a shop? You gave him a running engine'd car for a tranny swap. He gave you back a nonrunning car with a different tranny and you said, what? - that's OK, I'll pay you and take the car home? So how did his test drive go to verify the tranny is fully functioning in all gears and at all speeds, etc.......cough......?

engine stayed in, he only tested 1 2 5 and 6 and says they were all the same, pretty sketch on his end but he want me to tow the car away hasnt even mentioned me paying him anything more. and a little more the car was running perfectly and then one day when i was moving for the street sweeping the starter just kept spinning and it didnt pop out to grab the flywheel i took it to him with only that and the trans issue. the trans i bought from another source as well. but yes me and my other friend whos goin to school to become a mechanic are gonna try and diagnose it see if it was on him or not.

 

[bryanmk3]

quick update me and my friend went to check it out, didnt even need to compression test it. it sounds like a sewing machine and so much air is blowing out of the exhaust so our guess is that tensioner went out/ it jumped timing. and it also explains why the old starter still worked i thought the starter was just spinning in place but it was actually spinning the engine thats how low of resistance it had

 

[IdahoDoug]

Thanks for the added color. What it seems like now is he did the swap but dislodged something electrical, or fudged the starter replacement by not disconnecting the battery and having a hot wire touch something. Or my aforementioned engine CPU swap - anyone know if that's needed on the Supra for an auto to manual tranny swap? The reason I suspect electrical is he messed with some wiring to get this job done. There's a clutch interlock to prevent starting with the clutch engaged, to install the clutch in the firewall where none existed he may have needed to disconnect some wires or move them, perhaps he lowered the engine cradle some to get to the upper bellhousing bolts and stretched/snapped a wire or two. So that's my suspicion.

From here, it's a traditional sequence on the basics. Try starting it with a fresh battery and starter fluid. Nothing? You have no spark and that needs to be figured out. Did it start on the starter fluid and then die? You have a fuel problem. Disconnect a fuel line and have a fire extinquisher and a container to see if fuel gets pumped into the container. No? Check the wiring for the fuel pump. Also, check fuses in case my concern over a battery left connected and a hot wire happened. You might be able to see accumulated dust on the battery terminal bolts to "prove" it was left connected during a major vehicle service, which is a bad idea - especially that huge hot wire to the starter which was almost certainly removed.

Let us know what you find, and I hope this is solvable. It's no fun cleaning up someone else's mess. Oh, and the compression check was DEFINITELY done wrong if he lazily left two spark plugs in it. BTW, that also shows the mechanic could not start it and was clutching at straws by the time he opted to do a compression check (which for a car previously running is DEFINITELY grasping at straws.