Newby - needing help with diag
Thread Starter
Advanced
Joined: Mar 2023
Posts: 61
Likes: 13
From: Palm Beach County, FL
Newby - needing help with diag
Hello all, I just bought an ‘89 that has been sitting for at least a year or two. It spins over (so V.A.T.S. okay) but doesn’t run. Here is what I have done this week: new fuel pump and sock, new fuel filter, emptied tank of stale gas and added a few fresh gallons. 8 new injectors. I have verified that I have 42 PSI at key on and it drops to 39 or 40 while cranking. It holds 42 for a while with key off. The injectors are receiving a pulse (test light verified). The car has spark, the inside of the distributor cap appears used but normal. The plug wires are on the distributor in the right places, and they all go to their corresponding (correct) plug. WIth a paper clip on A and B I get only “12” and the fan comes on. HELP!
Oil Producer
Joined: Apr 2014
Posts: 9,375
Likes: 2,737
interesting and kudos for DOING your work before posting.
my thoughts
- verify timing. buy or make a piston stop for use on cyl1. verify the balancers timing line is in the right spot. google this to see how to do it. easy.
- spray starting fluid (carb clean works too) into throttle body see if it fires. be sure to use liberal amounts.
- possibly the coolant temp sensor that feeds the ecu f’d, does it smell rich like gas in cyls?
- check compression
- are you absolutely sure you are sparking?
-
my thoughts
- verify timing. buy or make a piston stop for use on cyl1. verify the balancers timing line is in the right spot. google this to see how to do it. easy.
- spray starting fluid (carb clean works too) into throttle body see if it fires. be sure to use liberal amounts.
- possibly the coolant temp sensor that feeds the ecu f’d, does it smell rich like gas in cyls?
- check compression
- are you absolutely sure you are sparking?
-
Thread Starter
Advanced
Joined: Mar 2023
Posts: 61
Likes: 13
From: Palm Beach County, FL
Thanks Viking
Spraying brake cleaner into the intake makes no difference. Confirmed spark at multiple plug wires. I pulled the connector off the temp sensor (near #6 plug) - no change.
Spraying brake cleaner into the intake makes no difference. Confirmed spark at multiple plug wires. I pulled the connector off the temp sensor (near #6 plug) - no change.
Pro
Joined: Feb 2009
Posts: 655
Likes: 164
From: Vancouver Washington
Some brake cleaners are not flammable these days.
You said the injectors are firing and you have spark. Have you pulled the spark plugs and checked their condition?
The first time I started my car after sitting some years some of the injectors were stuck open and totally flooded the engine. So much so that I had to change the oil because the level had gone up by nearly a quart and it smelled of gas.
You can put the gas pedal to the floor and crank the engine over. This tells the computer that the engine is flooded and will stop fuel flow so you can clear out fuel in the engine.
You said the injectors are firing and you have spark. Have you pulled the spark plugs and checked their condition?
The first time I started my car after sitting some years some of the injectors were stuck open and totally flooded the engine. So much so that I had to change the oil because the level had gone up by nearly a quart and it smelled of gas.
You can put the gas pedal to the floor and crank the engine over. This tells the computer that the engine is flooded and will stop fuel flow so you can clear out fuel in the engine.
Drifting
Joined: Jul 2022
Posts: 1,805
Likes: 365
From: Central Florida
Sensor between 6 & 8 is for gauge/dash only. The coolant temp sensor responsible for fuel air mix is at the front of the intake manifold below the throttle body. You can unplug the MAF to check it.
Last edited by Vets-Vet; Mar 31, 2023 at 01:39 PM.
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Thread Starter
Advanced
Joined: Mar 2023
Posts: 61
Likes: 13
From: Palm Beach County, FL
Very frustrating, at the rail it has fuel (42 lbs) and it has spark!
A compression test showed strong compression (155-181 PSI). The engine has less than 80k on it so I expected the compression to be good.
A compression test showed strong compression (155-181 PSI). The engine has less than 80k on it so I expected the compression to be good.
Thread Starter
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Joined: Mar 2023
Posts: 61
Likes: 13
From: Palm Beach County, FL
Yes, fresh fuel.
I checked the timing, and it is correct. This is very frustrating.
You always hear people say “You need air, fuel, and spark”. We’ll, this car has all three and no bueno!
I checked the timing, and it is correct. This is very frustrating.
You always hear people say “You need air, fuel, and spark”. We’ll, this car has all three and no bueno!
Thread Starter
Advanced
Joined: Mar 2023
Posts: 61
Likes: 13
From: Palm Beach County, FL
1989 M.Y. (build date Oct 88)
It spins over (so V.A.T.S. okay) but doesn’t run.
Here is what I have done:
FUEL: new fuel pump and sock, new fuel filter, emptied tank of stale gas and added a few fresh gallons. 8 new injectors. I have verified that I have 42 PSI at key on and it drops to 39 or 40 while cranking. It holds 42 for a while with key off. The injectors are receiving a pulse (test light verified).
SPARK: The car has spark, the inside of the distributor cap appears used but normal. The plug wires are on the distributor in the right places, and they all go to their corresponding (correct) plug. WIth a paper clip on A and B I get only “12” and the fan comes on.
MECHANICAL:
Compression is uniform across all cylinders except one is slightly down (within 13%). Timing is correct, distributor is installed correctly and rotor points to #1 when #1 is at TDC. A peek inside the valve cover shows rockers moving as expected while cranking.
It spins over (so V.A.T.S. okay) but doesn’t run.
Here is what I have done:
FUEL: new fuel pump and sock, new fuel filter, emptied tank of stale gas and added a few fresh gallons. 8 new injectors. I have verified that I have 42 PSI at key on and it drops to 39 or 40 while cranking. It holds 42 for a while with key off. The injectors are receiving a pulse (test light verified).
SPARK: The car has spark, the inside of the distributor cap appears used but normal. The plug wires are on the distributor in the right places, and they all go to their corresponding (correct) plug. WIth a paper clip on A and B I get only “12” and the fan comes on.
MECHANICAL:
Compression is uniform across all cylinders except one is slightly down (within 13%). Timing is correct, distributor is installed correctly and rotor points to #1 when #1 is at TDC. A peek inside the valve cover shows rockers moving as expected while cranking.
Melting Slicks
Joined: Jun 2014
Posts: 2,236
Likes: 498
From: NJ
You may have done this already, but check to make sure; Under your mechanical section add: check that both valves are closed when #1 is at TDC and rotor pointing to #1 on Dist. You could be out 180° on the firing order.
Looks like you have everything else covered.
Was there any backfiring while cranking?
Looks like you have everything else covered.
Was there any backfiring while cranking?
Drifting
Joined: Apr 2011
Posts: 1,925
Likes: 441
From: Albuquerque NM
I had a similar situation recently with my 1991 L98
spark verified with in line spark light checker
Fuel verified with pressure guage and by inference using starting fluid.
Ended up being timing. It would crank but not fire, not even pop.
I redid the timing from scratch. Cylinder 1 TDC using timing tab and valve spring position.
Good luck!
spark verified with in line spark light checker
Fuel verified with pressure guage and by inference using starting fluid.
Ended up being timing. It would crank but not fire, not even pop.
I redid the timing from scratch. Cylinder 1 TDC using timing tab and valve spring position.
Good luck!
Thread Starter
Advanced
Joined: Mar 2023
Posts: 61
Likes: 13
From: Palm Beach County, FL
The timing is correct - verified TDC and rotor position
I think the problem is weak spark. I can see spark out in the open but under pressure (compression) maybe there is none.
I think the problem is weak spark. I can see spark out in the open but under pressure (compression) maybe there is none.
Oil Producer
Joined: Apr 2014
Posts: 9,375
Likes: 2,737
OK, this comment reminds me of a situation i had in an 85. I had purchased a “new” second hand hei and swapped the coil into my original distributor.
I had the same thing but the odd time i could get it to smoke out the exhaust.
I made this video eons ago about how i figured out how to bench test the hei. it worked very well. and the spark was ultra weak sauce. i used another known-good coil and the spark was bright and snappy as a comparison.
This was realllly early days for me getting into the hobby and i was pretty proud that i didn't fry myself. i was wearing rubber boots just in case. little did i know at the time. unfortunately u cant see anything but you can get the drift. i just used vice grips to make the connections to a battery on the bench. if you google it im sure you find a quality video. i was rotating the drive gear by hand forwards and backwards. the compariosons on the coils was huge. it was actually sparking on both but the one was very weak. problem solved when installed the good one.
https://m.youtube.com/shorts/rc9b0prqzKs
I had the same thing but the odd time i could get it to smoke out the exhaust.
I made this video eons ago about how i figured out how to bench test the hei. it worked very well. and the spark was ultra weak sauce. i used another known-good coil and the spark was bright and snappy as a comparison.
This was realllly early days for me getting into the hobby and i was pretty proud that i didn't fry myself. i was wearing rubber boots just in case. little did i know at the time. unfortunately u cant see anything but you can get the drift. i just used vice grips to make the connections to a battery on the bench. if you google it im sure you find a quality video. i was rotating the drive gear by hand forwards and backwards. the compariosons on the coils was huge. it was actually sparking on both but the one was very weak. problem solved when installed the good one.
https://m.youtube.com/shorts/rc9b0prqzKs