Died and will not start
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
Likes: 9
From: Denver Colorado
Died and will not start
1991 L98, 6-speed - no mods.
I was driving along and the engine just quit.
It didn't buck or anything, it just stopped running like the coil died.
I had it towed home & here is what I have found & done-
- removed a spark plug and when the engine cranked, it sparked, but somewhat faintly. It also spewed fuel out of the spark plug hole (good fuel pressure there)
- checked the coil and it failed the tests so I replaced it.
- Reinstalled the coil & it still cranks but will not fire.
- Check the fuses
-added fuel
Suggestions on which direction I should go next? This was a sudden failure like a component/fuse/relay failed.
Maybe the ignition module?
I was driving along and the engine just quit.
It didn't buck or anything, it just stopped running like the coil died.
I had it towed home & here is what I have found & done-
- removed a spark plug and when the engine cranked, it sparked, but somewhat faintly. It also spewed fuel out of the spark plug hole (good fuel pressure there)
- checked the coil and it failed the tests so I replaced it.
- Reinstalled the coil & it still cranks but will not fire.
- Check the fuses
-added fuel
Suggestions on which direction I should go next? This was a sudden failure like a component/fuse/relay failed.
Maybe the ignition module?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
It could be an injector stuck open.
I think it's more likely that the fuel pressure regulator diaphragm has ruptured. When that happens fuel goes through the vacuum line into the plenum and then gets dumped into the cylinders. To check for this, remove the vacuum line from the FPR and turn on the ignition without starting the engine. If any fuel comes out of the FPR vacuum port then the diaphragm is ruptured. This can be a serious problem -- I had a fire when mine ruptured.
I think it's more likely that the fuel pressure regulator diaphragm has ruptured. When that happens fuel goes through the vacuum line into the plenum and then gets dumped into the cylinders. To check for this, remove the vacuum line from the FPR and turn on the ignition without starting the engine. If any fuel comes out of the FPR vacuum port then the diaphragm is ruptured. This can be a serious problem -- I had a fire when mine ruptured.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
Likes: 9
From: Denver Colorado
It could be an injector stuck open.
I think it's more likely that the fuel pressure regulator diaphragm has ruptured. When that happens fuel goes through the vacuum line into the plenum and then gets dumped into the cylinders. To check for this, remove the vacuum line from the FPR and turn on the ignition without starting the engine. If any fuel comes out of the FPR vacuum port then the diaphragm is ruptured. This can be a serious problem -- I had a fire when mine ruptured.
I think it's more likely that the fuel pressure regulator diaphragm has ruptured. When that happens fuel goes through the vacuum line into the plenum and then gets dumped into the cylinders. To check for this, remove the vacuum line from the FPR and turn on the ignition without starting the engine. If any fuel comes out of the FPR vacuum port then the diaphragm is ruptured. This can be a serious problem -- I had a fire when mine ruptured.
I'll check it out tomorrow- thanks !
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
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From: Denver Colorado
The latest-
I disconnected the vacuum line from the FPR and when I turned the ignition ON/fuelpump on it did NOT spew any fuel.
I then hooked a fuel pressure gauge to the fuel rail port and when the key turned on (and the fuel pump ran for 2 seconds) the fuel pressure went up to 30 psi, and then dropped to 0 when the pump went back OFF.
Fuel pressure remained at 0 when cranking.
Also, the oil definitely smells of gasoline, so I will be changing the oil & filter before it is run again as well as removing the spark plugs to pump any excess fuel out.
The FPR diaphragm kit is on order and I'm planning on changing that before going any farther.
Does it sound like the FPR diaphragm failed or the fuel pump?
I disconnected the vacuum line from the FPR and when I turned the ignition ON/fuelpump on it did NOT spew any fuel.
I then hooked a fuel pressure gauge to the fuel rail port and when the key turned on (and the fuel pump ran for 2 seconds) the fuel pressure went up to 30 psi, and then dropped to 0 when the pump went back OFF.
Fuel pressure remained at 0 when cranking.
Also, the oil definitely smells of gasoline, so I will be changing the oil & filter before it is run again as well as removing the spark plugs to pump any excess fuel out.
The FPR diaphragm kit is on order and I'm planning on changing that before going any farther.
Does it sound like the FPR diaphragm failed or the fuel pump?
Last edited by Rik O'Shay; Sep 4, 2014 at 12:22 PM.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
Likes: 9
From: Denver Colorado
I should probably just change the diaphragm for piece of mind since I ordered the part.
I'm really wondering about the fuel pump too- 30 PSI that is there for 2 seconds & then disappears and zero fuel pressure while cranking.
But a failed FPR might do that too...
Last edited by Rik O'Shay; Sep 4, 2014 at 12:41 PM.
Instructor
Joined: Sep 2005
Posts: 135
Likes: 12
I gotta say the only time my engine stock '89 auto coup died in 22 years and I had to tow it was exactly caused by what you've already found - the coil was bad.
Back then I couldn't figure it out because it had a spark - but I didn't check the strength of the spark, seemed that the mechanic took a long time to figure out that the coil was producing a weaker spark.
All that was needed was a new coil, I did change out the ignition module just in-case that may have burnt out the coil.
So to me it's puzzling that you most likely found the original culprit but it didn't fix the problem. Maybe double check to make sure you are getting a strong spark. I really doubt that you have 2 unrelated issues simultaneously causing a no start condition.
Back then I couldn't figure it out because it had a spark - but I didn't check the strength of the spark, seemed that the mechanic took a long time to figure out that the coil was producing a weaker spark.
All that was needed was a new coil, I did change out the ignition module just in-case that may have burnt out the coil.
So to me it's puzzling that you most likely found the original culprit but it didn't fix the problem. Maybe double check to make sure you are getting a strong spark. I really doubt that you have 2 unrelated issues simultaneously causing a no start condition.
Last edited by barrypaul2005; Sep 4, 2014 at 07:15 PM.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
Likes: 9
From: Denver Colorado
After researching the issue, I'm starting to think that it is the fuel pump, as it is only supplying 28 psi when I turn the key on and 0 pressure when cranking.
Today I pulled the spark plugs and all of them were wet. I cranked the engine and cleared out the cylinders. After the excess spewed out a fine mist (as I think it should) appeared.
I also drained the oil and it was thin and smelled strongly of gas.
What puzzles me most is that the fuel pressure regulator does not spew any fuel from the vacuum line at any time, key on or cranking.
So what I think I will do is to replace the fuel pump & strainer & then go from there. The low startup & cranking pressure tells me that the pump isn't providing adequate pressure and I need to fix that 1st.
Today I pulled the spark plugs and all of them were wet. I cranked the engine and cleared out the cylinders. After the excess spewed out a fine mist (as I think it should) appeared.
I also drained the oil and it was thin and smelled strongly of gas.
What puzzles me most is that the fuel pressure regulator does not spew any fuel from the vacuum line at any time, key on or cranking.
So what I think I will do is to replace the fuel pump & strainer & then go from there. The low startup & cranking pressure tells me that the pump isn't providing adequate pressure and I need to fix that 1st.
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Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
Likes: 9
From: Denver Colorado
Today I installed a new fuel pump.
Before it would pressurize to 28 psi & then immediately drop to 0 psi when the pump turned off.
With the new pump it pressurizes to about 45 psi & the pressure remains.
But it still won't start.
Installed new plugs & wires but think I may still have a coil problem as both the new & old coils fail the tests between the center post & the batt & tach points- it's open each place.
So I have a new cap/coil/& rotor on the way & will give them a go when they arrive next week.
Before it would pressurize to 28 psi & then immediately drop to 0 psi when the pump turned off.
With the new pump it pressurizes to about 45 psi & the pressure remains.
But it still won't start.
Installed new plugs & wires but think I may still have a coil problem as both the new & old coils fail the tests between the center post & the batt & tach points- it's open each place.
So I have a new cap/coil/& rotor on the way & will give them a go when they arrive next week.
Instructor
Joined: Mar 2007
Posts: 173
Likes: 18
From: Edinburgh Midlothian
Today I installed a new fuel pump.
Before it would pressurize to 28 psi & then immediately drop to 0 psi when the pump turned off.
With the new pump it pressurizes to about 45 psi & the pressure remains.
But it still won't start.
Installed new plugs & wires but think I may still have a coil problem as both the new & old coils fail the tests between the center post & the batt & tach points- it's open each place.
So I have a new cap/coil/& rotor on the way & will give them a go when they arrive next week.
Before it would pressurize to 28 psi & then immediately drop to 0 psi when the pump turned off.
With the new pump it pressurizes to about 45 psi & the pressure remains.
But it still won't start.
Installed new plugs & wires but think I may still have a coil problem as both the new & old coils fail the tests between the center post & the batt & tach points- it's open each place.
So I have a new cap/coil/& rotor on the way & will give them a go when they arrive next week.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
Likes: 9
From: Denver Colorado
Check the coil earth tab for continuity, I had the same issue and when I fitted the new coil I found that the earth strap wasn't making a good connection, this can also cause issues with the module, so I would recommend changing it too, it is also worth checking the circuit board harness (3 wires from the back of the distributor.)
I have checked the old coil & the new Autozone coil (I bought for troubleshooting) and get failures on both when checking from the Batt or Tach leads to the center nubb, so either the coils are both bad or the nubb is bad. I have 12 volts to the ditributor so I know the supply voltage is good.
A new AC Delco cap & rotor set on the way as well as new 50,000 volt coil coming from Jegs. I have new Moroso 8.8 mm wires (very nice wire set) & new AC Delco Platinum plugs so the ignition system will be all new except the ignition module.
I also installed a new battery yesterday as the one I had load tested bad.
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
From your description it sounds like the pump was the heart of your issue, sometimes they just quit like that. Mine was at a stop light, and it acted like it ran out of gas, well it did in a way. But cruising down the road, I could see it clrearing the lines pretty quickly.
For your spark, I wonder how much effect the old battery had. Did you try starting it with the new battery?
For your spark, I wonder how much effect the old battery had. Did you try starting it with the new battery?
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
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From: Denver Colorado
Once I install the new ignition parts I should be good to go. I might replace the ignition module if the new parts don't fix the starting issue.
After that I will be taking it to a Corvette Specialist.....
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
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From: Denver Colorado
I couldn't wait for the new parts to come so I picked up a new cap, rotor, and coil and installed them.
I have good spark, will not start and flooding the cylinders.
looking at the FSM the fuel system diagnosis points to the fuel pressure regulator but mine is not leaking through the vacuum port and pressure remained steady45-50 psi.
Right now I'm at a loss as to why the fuel is flooding the cylinders.
Wondering if a computer is sending bogus On commands to the injectors....
I have good spark, will not start and flooding the cylinders.
looking at the FSM the fuel system diagnosis points to the fuel pressure regulator but mine is not leaking through the vacuum port and pressure remained steady45-50 psi.
Right now I'm at a loss as to why the fuel is flooding the cylinders.
Wondering if a computer is sending bogus On commands to the injectors....
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Second, flooding is probably most likely to by caused by a faulty Coolant Temp sensor. Test that. Here are the values for testing:
Third, you can check and see if the computer is sending bogus On commands to the injectors; With the Key on, check for continuity between the injector plug pin and ground. If you have continuity, the ECM would be holding the injectors wide open, which would flood it quick.
Last, You can remove the plenum/FPR w/o draining coolant; clamp the TB coolant lines w/a clamp, then remove them. I bet you could even unbolt the TB from the plenum and leave it in place, remove the plenum too.
Last edited by Tom400CFI; Sep 6, 2014 at 09:03 PM.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
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From: Denver Colorado
I will put the FP gauge on the test port tomorrow & make sure to get an accurate reading.
Is the temp sensor located on the head between #8 & #6 plugs? I made sure that was connected but will clean the contacts & test the resistance tomorrow.
Which pin? W would guess that one is already ground so it would be the other wire, right?
Will look at that.
Thanks for the advice guys!
Third, you can check and see if the computer is sending bogus On commands to the injectors; With the Key on, check for continuity between the injector plug pin and ground. If you have continuity, the ECM would be holding the injectors wide open, which would flood it quick.
Thanks for the advice guys!
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Unplug the harness from the sensor, and probe bot pins in the sensor receptacle. Using the chart above, approximate ambient temp and see if your ohm reading jibes w/the one in the chart for the appropriate temp.
Thread Starter
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From: Denver Colorado
great info- thanks!
I didn't have a lot of time to look at the car but I did check key ON fuel pressure- 42 PSI the after the 2 seconds dropping to and holding 40 PSI.
I found the coolant temp sensor but it's all bu itself, will check it tomorrow along with the injectors.
I did check each pin on one injector connector and it showed 700 + ohms to ground with the key on.
I didn't have a lot of time to look at the car but I did check key ON fuel pressure- 42 PSI the after the 2 seconds dropping to and holding 40 PSI.
I found the coolant temp sensor but it's all bu itself, will check it tomorrow along with the injectors.
I did check each pin on one injector connector and it showed 700 + ohms to ground with the key on.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 173
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From: Denver Colorado
I also checked each injector connector point to ground with the key on and they were all infinite/open.
Then I installed a new ignition control module, installed the plugs & wire and gave it a go-
It still did not start, but it did fire maybe one cylinder before returning to cranking only.
Now I'm starting to think the ECM.
Going out to pull the plugs again because I'm sure they are wet & the cylinders full of fuel.