my son's 87gt won't start so he called me. it cranks fine just doesn't even try to turn over. ran great till then. I started looking into it and so far I got about 45psi at fuel rail. and pulled a plug laid it on intake and got spark. next I placed cyl #1 at tdc and checked for roter at plug wire 1 position. any Ideas on where to go from here.
my son's 87gt won't start so he called me. it cranks fine just doesn't even try to turn over. ran great till then. I started looking into it and so far I got about 45psi at fuel rail. and pulled a plug laid it on intake and got spark. next I placed cyl #1 at tdc and checked for roter at plug wire 1 position. any Ideas on where to go from here.
Jumping a few thousands of an inch at atmospheric pressure means next to nothing. A healthy spark will easily jump a quarter inch gap outside of the combustion chamber.
Patrick is correct. A weak ignition system can produce spark when plug is inserted into the wire and grounded. When the plug is in the engine compression will not allow the weak system to produce a spark due to the high pressure between the plug electrodes. Also check the coil https://www.youtube.com/watch?v=xmdS4vGB-m8
You need spark (in the cylinder) and fuel to run. Use one of those transparent inline spark testers to see if you have spark. Put between coil and dist center. Throw some starting fluid down it's throat.
If it at least fires and you've got spark then it's fuel, no spark can be ignition module or coil. ICM is most likely. I've them just 'go' twice so far. Always carry a spare (and tools to swap it out) now. However if it's electrical, it could be a bad wire or connection somewhere that's just given up the ghost!
------------------ Anything I might say is probably worth what you paid for it, so treat it accordingly!
On two occasions separated by a few years, my '84 SE quit while driving and wouldn't restart. Both times showed strong spark with an inline tester. Both times displayed plenty of fuel in the TBI throat. Both times I replaced the ECM and it started immediately. Your results may vary...
[This message has been edited by David Hambleton (edited 01-01-2020).]
well I hooked up my spark tester to see how strong of a spark I really had and wasn't good...quarter inch if lucky. changed out the ignition module with a used one that I had laying around. tested it with ohm meter prior to install and same result. weak if any spark. decided to change icm with new and same result. ohmed out wiring from icm to ignition coil while bending it up and no breaks in it. pic up coil at 750 ohms. probably going to change out ignition coil with new for sanity sake. don't like to throw parts at it but gettin to that point.
Starter fluid and no bang indicates no spark in the cylinder. Apart from the coil, check the lead from the coil to the dist cap. It's unlikely all 6 of the ones from the dist to plugs all went bad at the same time Also check dist cap and the rotor.
------------------ Anything I might say is probably worth what you paid for it, so treat it accordingly!
yea, checked for continuity of coil plug wire but didn't ohm out. gonna do the cap and rotor as well. just odd ran fine then sat for couple days and now won't turn over. I did see the rotor lined up with #1plug wire at full compresson and at about 0-10deg. same with timing light while cranking. confused...
just changed the ignitiin coil, cap and rotor and I got it the fire up. Now for some reason that only has a miss. timing reading about 10deg. hooked up to my spark tester an all 6 fired good and strong. as I was testing wires 3,5 and 6 it ran really bad couldn't keep it running. One other part that I haven't changed was the pickup coil but it was reading about 750-800 ohms.
the pick up coil plug didnt look to good when i tested it. it was somewhat brittle. didn't know what kind of voltage goes through it or if it could be shorting out. although if so I would think it would be on random cylinders. odd parked it running fine then sat 3 days then wouldn't start.
thinking... do injectors 1,2 & 4 use the same wiring? when I test them for spark there is really no difference in the idle. when I test 3,5 & 6 it runs really bad thanks
I could be jumping to a conclusion. If you are confident in the condition of the plugs and wires, the next thing to look at is the injectors. If you disconnect one cylinder and the car runs worse, that cylinder is working properly. If you add starting fluid while the engine is running rough and it smooths out briefly, some injectors are not working.
had somewhat the same issue and found the fuel regulator was dumping fuel in the vacuum line. pull the vacuum line and try to crank the engine and see if you see fuel
no matter what plugs or wires I use it's always the same 3 cylinders that are misfiring. I have had a regulator go before and it was a random misfire and ran very rich. guess going to take the intake off today and look at the injectors and wirimg see what I can find.
just got the intake off and the 3 cylinders that I'm having problems with has a wet look to the carbon build up inside intake and the 3 others have are dry carbon. any ideas. they must be gettin fuel to be wet?
yea both 5amp injector fuses look good. cyl 1,2&4. have the issue. from what I remember pressure held above 40psi for about 5 min and slowly dropped for next 10 min.
that's crazy. parked car at night running fine. first thing in morning...rotor and injectors? gonna try to clean them up while I order new from rockauto.
yes it was turning over but not starting. finally.
got a chance to get back to working on it last night. I got the injectors out cleaned and tested them best I could. pressurized with carb cleaner, observed spray pattern and all ohmed out at 16.1. put everything back together with the injectors placed in opposite cylinders (good in the bad and bad in the good) to see if the problem moves to new cyl.
well the same cylinders are running bad. I checked the pressure at the rail with the return line pinched and it it is holding solid 65lbs. took 20 min to get down to 45 and stayed there. seems like the leaking injector thing was fixed. after removing clamp off the line the pressure dropped to 20 within couple min. now it seems like another problem in the tank.
it still runs like crap and the same 3 cyl are acting up even after swapping injectors. pressure on start up and idling is 40psi. shouldn't that be enough to feed injectors? did notice the 3 cyl that run bad are at the far side of the rail if that means anything.
i know I have to move to the tank next. shouldn't the 40psi hold an idle? how do you go about problem in the tank?
compression checked out all cylinders about 130-140 psi.
upon doing test I decided to put screwdriver from injector to my ear and the cylinders that I'm having a problem with aren't ticking thru the screwdriver. think I found my problem. any idea how to attack that problem?