85 cranks but will not start
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Joined: Feb 2003
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From: biloxi ms
85 cranks but will not start
my 85 will crank but not start, I went out to move it when I started it the car started fine then died but started right back up, then later that day I went to drive it and it will crank but not start, it trys an will run for a second at times after it sits a while. I installed a new fuel pump has 39 psi at the rail and checked spark at the wires with the old screw driver trick and had spark. any one have this problem before.
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Re: 85 cranks but will not start (85redvette)
It could be the ECM, but first check both inj fuses. The ECM won't pulse the injectors if it doesn't receive timing pulses from the distributor.
Drifting
Joined: Feb 2002
Posts: 1,952
Likes: 2
From: Little Rock Arkansas
Re: 85 cranks but will not start (jfb)
Make sure the fuel pump is getting the signal from the oil pressure sensor... The ECM will not activate the fuel pump relay if the sensor is malfunctioning or not seeing oil pressure upon cranking...
Instructor
Joined: Jan 2003
Posts: 173
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From: Warren MI
Re: 85 cranks but will not start (jfb)
Being an ASE Master Recertified Tech / Advanced Driveability Specialist, the first thing I would say is "remember the basics" = you need 3 things to light an engine:
-compression
-fuel
-ignition
That being said - which is missing? Next time it acts up, check this:
Hit it with some carb clean spray or ether - does it light and die? If so you have a fuel issue of various sorts.
If it is unresponsive to "artificial fuel supply", take a very close look at the ignition system - just because it will spark with the ol' screw driver trick, doesn't mean it is actually getting spark in a pressurized cylinder. I have been "burned" by this a couple of times! As the pressure level increases in a combustion chamber, so does firing resistance = check for a burned through rotor arcing to the distibutor shaft and such... :banghead:
-compression
-fuel
-ignition
That being said - which is missing? Next time it acts up, check this:
Hit it with some carb clean spray or ether - does it light and die? If so you have a fuel issue of various sorts.
If it is unresponsive to "artificial fuel supply", take a very close look at the ignition system - just because it will spark with the ol' screw driver trick, doesn't mean it is actually getting spark in a pressurized cylinder. I have been "burned" by this a couple of times! As the pressure level increases in a combustion chamber, so does firing resistance = check for a burned through rotor arcing to the distibutor shaft and such... :banghead:
Thread Starter
Cruising
Joined: Feb 2003
Posts: 14
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From: biloxi ms
Re: 85 cranks but will not start (Hydratech Braking)
Thanks for the inputs, I have checked the basics. the plugs are getting wet from fuel and I tried spraying the carb cleaner to see if it would run on it with no luck. that puts me back to the spark, going to replace rotor car and coil and hope for the best
Instructor
Joined: Jan 2003
Posts: 173
Likes: 1
From: Warren MI
Re: 85 cranks but will not start (85redvette)
Once a spark plug becomes completely fuel soaked, it will not fire correctly. Make sure you also install a fresh set of spark plugs... :banghead:
Also, if it has flooded very badly, you may also want to change the engine oil as it may have become extremely fuel diluted and may not lubricate correctly...
[Modified by Hydratech Braking, 3:30 AM 2/16/2003]
Also, if it has flooded very badly, you may also want to change the engine oil as it may have become extremely fuel diluted and may not lubricate correctly...
[Modified by Hydratech Braking, 3:30 AM 2/16/2003]
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From: North Yorkshire, England
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Re: 85 cranks but will not start (jburnett)
Can you tell me where you came by this information?
Make sure the fuel pump is getting the signal from the oil pressure sensor... The ECM will not activate the fuel pump relay if the sensor is malfunctioning or not seeing oil pressure upon cranking...
Safety Car
Joined: Mar 2000
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From: Anderson, IN
Re: 85 cranks but will not start (85redvette)
If you're not getting any spark, I would inspect the cap and rotor, and I would check out the coil with a multi-meter, if that all checks good, I would have the ignition module checked (Autozone will do it for free, but I've heard bad things about their quality; although mine has been running ok for about a year.) I'm pretty sure that the 85's ignition system is still pretty simple, like not too much input from the computer. If you have the ignition on, you should have power to the distributor and it should spark if everything inside it is working.
Team Owner
Joined: Mar 2001
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From: Cincinnati, Oh USA
Re: 85 cranks but will not start (Ray Quayle)
The fuel pump circuit is in the electrical diagnosis service manual supplement.
When you crank your engine the ECM turns on the fuel pump for 2 seconds and if the engine catches, an oil pressure switch supplies power to the fuel pump.
When you crank your engine the ECM turns on the fuel pump for 2 seconds and if the engine catches, an oil pressure switch supplies power to the fuel pump.
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From: North Yorkshire, England
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Re: 85 cranks but will not start (jfb)
jfb, Maybe I pick too many nits. ;) What he said was "Make sure the fuel pump is getting the signal from the oil pressure sensor... The ECM will not activate the fuel pump relay if the sensor is malfunctioning or not seeing oil pressure upon cranking...", the ECM will activate the fuel pump relay if the sensor is not seeing oil pressure upon cranking. The ECM actually activates the fuel pump relay for 2 seconds if there is no crank and continuously while cranking (receiving distributor reference pulses). I didn't want it to sound like I didn't think the problem could be the oil pressure switch, it's just that jburnett's statement was a little misleading. Just wanted to check the source.
The fuel pump circuit is in the electrical diagnosis service manual supplement.
When you crank your engine the ECM turns on the fuel pump for 2 seconds and if the engine catches, an oil pressure switch supplies power to the fuel pump.
When you crank your engine the ECM turns on the fuel pump for 2 seconds and if the engine catches, an oil pressure switch supplies power to the fuel pump.
Thread Starter
Cruising
Joined: Feb 2003
Posts: 14
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From: biloxi ms
Re: 85 cranks but will not start (Ray Quayle)
Update, I changed out the coil the car will start now but have to hold the pedal 1/2 way down to keep it running, it back fires a bit through the exhaust.
:banghead:
:banghead:
