Hard start when warm
Thread Starter
Instructor
Joined: Aug 2009
Posts: 146
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From: Broadway Virginia
Hard start when warm
1988 Coupe. When cold the car starts immediately when the key is turned. Problem, (what I 've noticed), is when car is warm/hot the engine takes longer to start, up to five seconds of cranking.
I do not believe that this is a starter hot soak issue as it cranks fine and at the same speed hot or cold.
I suspect either an ignition or fuel injector problem. But do not know.
Anybody have this and get it resolved? Any ideas?
Thanks in advance.
WSS
I do not believe that this is a starter hot soak issue as it cranks fine and at the same speed hot or cold.
I suspect either an ignition or fuel injector problem. But do not know.
Anybody have this and get it resolved? Any ideas?
Thanks in advance.
WSS
Racer
Joined: Feb 2004
Posts: 251
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From: De Pere WI
93LT1 and I have the same problem. A mechanic I know said when he heard it crank he thought fuel pump. I checked fuel pressure and pressure is good but leaks down in less than two hours. That is the only effort I put into the problem. I keep saying one of these days I will look into it. A leaking injector would wash out the plug. Pull plugs and one would be way diffrent.
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
A common part that causes your symptoms is a spark module in the distrubutor that makes weak spark when hot and recovers when it cools. Compare the intensity of spark between cranking cold and then hot to determine if it is the module.
Safety Car
Joined: Jan 2008
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From: Vero Beach Florida
I would look at fuel system first, do a pressure test for leak down and a ohm reading test on the injectors hot and cold. There have been lots of threads on this and you should find help also using search. Let us know what your readings are.
Racer
Joined: Jun 2001
Posts: 377
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From: Chicago IL
Having been through this one before, I agree that it is probably fuel related. check the pressure (lots of threads). If you are losing pressure immediately, there are a few suspect areas. I had a couple of bad injectors - but the main problem for my hard start was a leaking fuel pulsator. this is a relatively easy fix, pull the pump and replace the pulsator with a short section of fuel hose. after diagnosing everything and pulling my hair out, this simple one turned out to be the culprit. pressure holds now as it should and my hard start when warm is much, much better.
Thread Starter
Instructor
Joined: Aug 2009
Posts: 146
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From: Broadway Virginia
The ignition module was replaced in 1994. I just received a fuel pressure gauge and I will look up the procedure for the leak down test as well as the ohm reading of the injectors.
Once I have more information I will let you all know what I find.
FWIW, the car only has 22K miles and until recently was not driven very much at all.
Once I have more information I will let you all know what I find.
FWIW, the car only has 22K miles and until recently was not driven very much at all.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
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From: backwoods upstate ny
quickie test
five second start delay at both cold and hot start is probly fuel pressure leaking down...hot start delay only is likely electrical, most likely perp is the ign module inside the dizzy (i carry a spare ign module and tools to change in all my HEI equipped cars)
test for fuel pressure leakdown is best done with a pressure gauge... but quik test can be done by just 'cranking' engine three short bursts with momentary (3 to 5 sec) pauses in between, if engine fires off on third or fourth burst it's because pressure has 'built up'.
my LT-1 powered buick roaddie has had 'start delay' /failed the 'quik test' (no start till third burst) for several months now, gas mileage/power both fine, will fix it 'next week'.
test for fuel pressure leakdown is best done with a pressure gauge... but quik test can be done by just 'cranking' engine three short bursts with momentary (3 to 5 sec) pauses in between, if engine fires off on third or fourth burst it's because pressure has 'built up'.
my LT-1 powered buick roaddie has had 'start delay' /failed the 'quik test' (no start till third burst) for several months now, gas mileage/power both fine, will fix it 'next week'.
Last edited by redrose; Oct 6, 2009 at 02:16 PM.
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Safety Car
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five second start delay at both cold and hot start is probly fuel pressure leaking down...hot start delay only is likely electrical, most likely perp is the ign module inside the dizzy (i carry a spare ign module and tools to change in all my HEI equipped cars)
test for fuel pressure leakdown is best done with a pressure gauge... but quik test can be done by just 'cranking' engine three short bursts with momentary (3 to 5 sec) pauses in between, if engine fires off on third or fourth burst it's because pressure has 'built up'.
my LT-1 powered buick roaddie has had 'start delay' /failed the 'quik test' for several months now, gas mileage/power both fine, will fix it 'next week'.
test for fuel pressure leakdown is best done with a pressure gauge... but quik test can be done by just 'cranking' engine three short bursts with momentary (3 to 5 sec) pauses in between, if engine fires off on third or fourth burst it's because pressure has 'built up'.
my LT-1 powered buick roaddie has had 'start delay' /failed the 'quik test' for several months now, gas mileage/power both fine, will fix it 'next week'.
five second start delay at both cold and hot start is probly fuel pressure leaking down
**most likely as i have the same problem with my 88 and just simply live with it.
...hot start delay only is likely electrical,
**i disagree, fuel related is my vote.
most likely perp is the ign module inside the dizzy (i carry a spare ign module and tools to change in all my HEI equipped cars)
***nope, i disagree here too. somewhat unrelated; i had replaced my ignition module 8+ times for a no start situation and found that even though the inside of my distributor is clean - bright - shiny, there was a bad ground connection for the module itself. i sanded down the connection and it has so far worked flawlessly. i think that the injectors in your case and possible mine since i have good pressure and no fast leak-down is the problem.
test for fuel pressure leak-down is best done with a pressure gauge... but quik test can be done by just 'cranking' engine three short bursts with momentary (3 to 5 sec) pauses in between, if engine fires off on third or fourth burst it's because pressure has 'built up'.
**obviously do this when hot as the 88's have a csv that doesn't drop out until a certain temp is reached. also, the pressure should have "built up" w/i 2 seconds after the key is turned to the "on" position.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
Originally Posted by Da Mail
[B
[B
there was a bad ground connection for the module itself. i sanded down the connection . [/B]
88's have a csv that doesn't drop out until a certain temp is reached. also, the pressure should have "built up" w/i 2 seconds after the key is turned to the "on" position.
88's have a csv that doesn't drop out until a certain temp is reached. also, the pressure should have "built up" w/i 2 seconds after the key is turned to the "on" position.
module grounding is by one or both of the two screws that hold the module down (varies with module mfrs)...what did you 'sand down'?
Last edited by redrose; Oct 6, 2009 at 11:41 AM.
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csv sensor 'times out' thru internal 'warp switch' after nominal 8 sec when coolant is -5*F and timeout reduces as coolant warms, at ~95*F coolant the sensor is always 'open' (no csv call)...1-2 sec of pump operation may NOT bring pressure to 'run' level if system was at 0 psi initially, in my experience, hence my 'three strike' method which avoids starter motor overheat of long crank while using 'human factor' delay in turning key to run pump...actually, i now have modded the procedure with my roaddie to reduce component strain but may be too complex for some.
module grounding is by one or both of the two screws that hold the module down (varies with module mfrs)...what did you 'sand down'?
module grounding is by one or both of the two screws that hold the module down (varies with module mfrs)...what did you 'sand down'?
csv sensor 'times out' thru internal 'warp switch' after nominal 8 sec when coolant is -5*F and timeout reduces as coolant warms, at ~95*F coolant the sensor is always 'open' (no csv call)...
**totally aware of this
1-2 sec of pump operation may NOT bring pressure to 'run' level if system was at 0 psi initially,
**mine does and everyones should also (imo).
in my experience, hence my 'three strike' method which avoids starter motor overheat of long crank while using 'human factor' delay in turning key to run pump...actually, i now have modded the procedure with my roaddie to reduce component strain but may be too complex for some.
module grounding is by one or both of the two screws that hold the module down (varies with module mfrs)...what did you 'sand down'?
**i sanded the internal "base" of the distributor on the inside where any portion of the ignition module or capacitor attaches even though it was bright and shiny...never thought that something so damned clean could cause this but, it did FOR SURE.
Last edited by Da Mail Man; Oct 6, 2009 at 02:27 PM. Reason: spelling correction
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
*************************************
**i sanded the internal "base" of the distributor on the inside wher any portion of the ignition module or capacitor attaches even though it was bright and shiny...never thought that something some damned clean could cause this but, it did FOR SURE.
**i sanded the internal "base" of the distributor on the inside wher any portion of the ignition module or capacitor attaches even though it was bright and shiny...never thought that something some damned clean could cause this but, it did FOR SURE.
'sanding' the module and dizzy base is 'interesting'...likely would increase 'surface area' of htc contact and aid heat transfer...i have observed temp rise vs time of modules on my 'allen' dizzy tester with/without htc and will investigate 'sanding' when winter wins.
btw, in an emergency, even 'chassis lube' (grease) is 'better than nothing' under the ign module.
Safety Car
Joined: Jul 2004
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where the ign module sits on the dizzy base, you MUST use 'heat transfer compound' (aka grease) to reduce the internal temp of the ign module , without any htc the module life expectancy will be reduced significantly (only minutes perhaps))...htc is a good heat transmitter but electrically a poor conductor...use new ign module hold-down screws to get a good elec ground, or at minimum remove corrosion from old screws before re-use (altho removing the corrosion-resistant coating from the old screws at the same time is almost unavoidable)...always inspect used modules for corrosion in the mounting screw seat area as this is common due to normal high levels of ozone inside the dizzy cap...typically the screw threads in the dizzy base are shiny after the old screws are turned out, but 'chase' those threads if in doubt.
'sanding' the module and dizzy base is 'interesting'...likely would increase 'surface area' of htc contact and aid heat transfer...i have observed temp rise vs time of modules on my 'allen' dizzy tester with/without htc and will investigate 'sanding' when winter wins.
btw, in an emergency, even 'chassis lube' (grease) is 'better than nothing' under the ign module.
'sanding' the module and dizzy base is 'interesting'...likely would increase 'surface area' of htc contact and aid heat transfer...i have observed temp rise vs time of modules on my 'allen' dizzy tester with/without htc and will investigate 'sanding' when winter wins.
btw, in an emergency, even 'chassis lube' (grease) is 'better than nothing' under the ign module.
*************************************
where the ign module sits on the dizzy base, you MUST use 'heat transfer compound' (aka grease) to reduce the internal temp of the ign module
**I ALREADY KNOW THIS...it helps with the heat transfer and fills in the microscopic holes that would not usually come in contact with the distributor base which will in turn increase the total amount of surface area that the transfer can occur!
, without any htc the module life expectancy will be reduced significantly (only minutes perhaps))...htc is a good heat transmitter but electrically a poor conductor
**heat transfer gel is only that, for heat and nothing else...it has NO electrically conductive properties at all.
...use new ign module hold-down screws to get a good elec ground,
***as in my case, i did use the screws (of course!!) however, like i previously stated, it was ONLY AFTER i sanded the bright shiny finish of the inside of the internal distributor base, was i able to get the desired results. tightening down the screws PROPERLY made no difference and over time the connection to ground ELECTRICALLY broke down causing a NO SPARK situation.
or at minimum remove corrosion from old screws before re-use
**no corrosion on any of my screw hardware.
(altho removing the corrosion-resistant coating from the old screws at the same time is almost unavoidable)...always inspect used modules for corrosion in the mounting screw seat area as this is common due to normal high levels of ozone inside the dizzy cap...typically the screw threads in the dizzy base are shiny after the old screws are turned out, but 'chase' those threads if in doubt.
'sanding' the module and dizzy base is 'interesting'...
**wow!, you are waaayyy of base!!..i NEVER SAID THAT! i said (again) that i sanded the internal base of THE DISTRIBUTOR at the ground(s) and nothing else!..nobody in their right mind should EVER sand an ignition module!
likely would increase 'surface area' of htc contact and aid heat transfer...
**not on your life!..sanding any portion of the ignition module is ridiculous and has NOTHING do do with heat transfer or increasing "surface area"!!!!
i have observed temp rise vs time of modules on my 'allen' dizzy tester with/without htc and will investigate 'sanding' when winter wins.
**if you are intent on "sanding" your module, start saving up as you will be buying a replacement in no time!
btw, in an emergency, even 'chassis lube' (grease) is 'better than nothing' under the ign module.
**no, it is not!..it will only serve to put a "blanket" so-to-speak between the heat that needs to be drawn off of the module and the destination it needs to go - the distributor base as a heat sink!
***besides, the o.p states that he has a hard start and not a no start situation and all this seemingly may not apply!***
Last edited by Da Mail Man; Oct 6, 2009 at 05:55 PM. Reason: spelling
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
L98's have some propensity for leaking THRU the pressure reg into the plenum (regulator diaphram failure, see local napa for new diaphragm)...pull the hose between the reg and plenum and sniff for gasoline odor, should NOT be any.
Last edited by redrose; Oct 6, 2009 at 03:23 PM.
Thread Starter
Instructor
Joined: Aug 2009
Posts: 146
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From: Broadway Virginia
I have not had time to check hot and cold injector OHMS and fuel pressures yet, but I want to get the theory understood. If the injectors are warm/hot they are more likely to leak if they are going to?
And, if they leak down it causes a rich /flooded condition that will cause dark exhaust when it does start? And, due to the loss of line/rail pressure at first it causes an extended crank until pressure can be built back up?
FWIW I had the fuel filter replaced two years ago. I have never had a NO START condition. It just takes longer when warm.
And, if they leak down it causes a rich /flooded condition that will cause dark exhaust when it does start? And, due to the loss of line/rail pressure at first it causes an extended crank until pressure can be built back up?
FWIW I had the fuel filter replaced two years ago. I have never had a NO START condition. It just takes longer when warm.
Last edited by walter schweigert; Oct 6, 2009 at 10:28 PM.
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From: Vero Beach Florida
At the top of the Tech section look for the sticky from FIC, also if you search you will find a lot of information also.
http://forums.corvetteforum.com/c4-t...ctor-ohms.html
http://forums.corvetteforum.com/c4-t...ctor-ohms.html
Last edited by floridamale; Oct 6, 2009 at 10:44 PM.
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Put a fuel pressure gauge on the shrader valve at the end of the right fuel rail and turn the ignition on for longer than 2 seconds. You should get 35-42 psi and after the ignition is off, it shouldn't lose pressure rapidly (minutes). You can do it hot too. Injectors usually run about 16 ohms and this should get higher when hot, not lower. A much better electrical test is to measure their inductance and Q with an impedance bridge, I found a bad injector coil this way whose d.c. resistance didn't change but the inductance halved and the Q also halved. Only about 3 people on this forum even knows what an impedance bridge is.
Oh, did you check the spark like I recommended in my first post?
Oh, did you check the spark like I recommended in my first post?