truck fires when letting off the key? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jimmybeus · 04-03-2010, 01:02 AM

Ok I am puzzled now. I picked up a 1986 short bed 4x4 that the po thought that the motor was blown for $500. He thought the rear main was out. Turns out the oil filter housing was broke and the filter wasn't seating properly and all the oil was pouring out. I fixed that but still wouldn't run. Turned over fine but no spark. Replaced the control mod in the distributor. Would turn over but still no spark. Took distributor apart again and checked everything out again, everything checked out fine. I put it together and tried it again. Turned over fine but right as I let OFF the key is when it fired. Tried it a few more times same thing, turn over all day long pressing key all the way down but will only fire right as I'm am letting off. I replaced the ignition switch on the base of the column, same thing. I adjusted up and down same thing. I put in a new key switch in this evening hoping that would fix it but still the same thing. What else could it be? Sorry this is so long but I am stumped and I have fixed everything I thought it could be what am I missing? Thanks in advance.

James McClure · 04-03-2010, 05:49 AM

Jimmy. Does it have "ESC"? 4 wire pigtail comming out of the dist. If there is, there is a procedure to run it with the wire unplugged, but I don't know what it is off hand. If it's not "ESC" and only has a 3 wire connector pluged into the cap along with the pink wire I can help you with some checks. First, key on, is there B+ on the pink wire? Next, especially if a cap was repalced, are there a total of 4 connnections at the plug in on the cap? Very often people forget or miss moving the ground tab to the new cap for the coil. Look at the pickup coil wireing (green & white) under the rotor. Give each one a "tug" don't pull hard, just a tug. They tend to break inside the insulation because of the constant movement of the vac advance. Hope this helps, and sorry I don't have info on ESC. Jim

spinem · 04-03-2010, 09:57 PM

im just gonna throw it out there....

timing is on?

87chevy.com · 04-03-2010, 11:25 PM

quick way to check to see if the dist. is 180 off is to put the motor on tdc compression on #1 and see if the rotors pointing to #1.. if not theres a start.

cableguy0 · 04-03-2010, 11:46 PM

Check the neutral safety switch. Assuming it ran at one time and wasnt touched because of the oil issue. The timing should at least be close enough to run. If its lack of fire you need to check the electrical stuff. These trucks are pretty straight forward. With the key in the on position check to see if you have 12 volts at the power wire for the distributor. Next step is to have someone crank the truck while you check to see if you have 12 volts at the distributor power wire. No sense in changing a bunch of stuff without looking for the problem.

jimmybeus · 04-04-2010, 08:05 PM

Thanks for the advice. The timing is on, I can get it to run and drive it around. It does run really good, no misses or anything like that. I have checked to see if the ground clip is in the distributor(I am assuming that I am looking at the right part). It is just a pain to let off the key at the right moment to get it to run. I guess for 500 bucks there will be a few issues. Any other thoughts? Thanks.

westofb · 04-04-2010, 11:51 PM

still sounds like igintion switch prob to me. did you install a brand new one, or another used one? By what you are saying, you are not getting power to the distributor in the start position, only in the run position. Someone mentioned neutral safety switch, I doubt that is the problem, that should only prevent the the engine from cranking. Have you checked all the fuses in the under dash fuse panel? I cant remember for sure off top of my head, but there may be a blown fuse, one that is only hot in the when the key is in the start postion. Good luck getting it going.

rfmaster · 04-05-2010, 01:25 AM

Based on your description it appears that ignition coil is not getting +12V during cranking, but does when ignition key is in RUN position. As always, assume nothing - question everything - get your DVM or a test light and verify that coil receives +12 V when ignition key is in run and crank positions. Worn ignition key contacts are usual suspects.

//RF

**PRattenbury** · 04-05-2010, 03:07 AM

Starter motor wiring. Check the solenoid wiring on the run and start tabs.

jimmybeus · 04-12-2010, 07:34 PM

Well I got it fixed. The coil was not getting power while it was cranking. Found a cut wire by the fuse box that had power while key was on and while cranking so I tapped on that one and it works great. Thanks for the ideas.

04-03-2010, 05:49 AM	#2
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: truck fires when letting off the key? Jimmy. Does it have "ESC"? 4 wire pigtail comming out of the dist. If there is, there is a procedure to run it with the wire unplugged, but I don't know what it is off hand. If it's not "ESC" and only has a 3 wire connector pluged into the cap along with the pink wire I can help you with some checks. First, key on, is there B+ on the pink wire? Next, especially if a cap was repalced, are there a total of 4 connnections at the plug in on the cap? Very often people forget or miss moving the ground tab to the new cap for the coil. Look at the pickup coil wireing (green & white) under the rotor. Give each one a "tug" don't pull hard, just a tug. They tend to break inside the insulation because of the constant movement of the vac advance. Hope this helps, and sorry I don't have info on ESC. Jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

04-03-2010, 09:57 PM	#3
spinem haha, ford guys... Join Date: Feb 2007 Location: Visalia, CA Posts: 576	Re: truck fires when letting off the key? im just gonna throw it out there.... timing is on?

04-03-2010, 11:25 PM	#4
87chevy.com BMW & ASE Master Certified Join Date: Feb 2004 Location: Houston, Texas Posts: 1,266	Re: truck fires when letting off the key? quick way to check to see if the dist. is 180 off is to put the motor on tdc compression on #1 and see if the rotors pointing to #1.. if not theres a start. __________________ 1987 Silverado - L83 5.3 w/ 6L80e ,A/C,P/W,P/L,TILT, HID projectors, Wilwood C-10 Pro Spindles w/ 2018 silverado front brakes & C-5 Corvette Rear Disc Brakes 1999 BMW 528i - 5.7 LS1 w/ 4l60e, Ford 8.8 IRS w31 spline posi & FX-r projector retrofit New project: 2006 BMW x5 6cyl AWD to L83 6l80e 4wd to 2WD / RWD A poor man buy's it twice finally got my domain name back, 87chevy.com.... site rework in progress

04-03-2010, 11:46 PM	#5
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: truck fires when letting off the key? Check the neutral safety switch. Assuming it ran at one time and wasnt touched because of the oil issue. The timing should at least be close enough to run. If its lack of fire you need to check the electrical stuff. These trucks are pretty straight forward. With the key in the on position check to see if you have 12 volts at the power wire for the distributor. Next step is to have someone crank the truck while you check to see if you have 12 volts at the distributor power wire. No sense in changing a bunch of stuff without looking for the problem. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-04-2010, 08:05 PM	#6
jimmybeus Registered User Join Date: Nov 2008 Location: La Barge Wyoming Posts: 63	Re: truck fires when letting off the key? Thanks for the advice. The timing is on, I can get it to run and drive it around. It does run really good, no misses or anything like that. I have checked to see if the ground clip is in the distributor(I am assuming that I am looking at the right part). It is just a pain to let off the key at the right moment to get it to run. I guess for 500 bucks there will be a few issues. Any other thoughts? Thanks.

04-03-2010, 01:02 AM	#1
jimmybeus Registered User Join Date: Nov 2008 Location: La Barge Wyoming Posts: 63	truck fires when letting off the key? Ok I am puzzled now. I picked up a 1986 short bed 4x4 that the po thought that the motor was blown for $500. He thought the rear main was out. Turns out the oil filter housing was broke and the filter wasn't seating properly and all the oil was pouring out. I fixed that but still wouldn't run. Turned over fine but no spark. Replaced the control mod in the distributor. Would turn over but still no spark. Took distributor apart again and checked everything out again, everything checked out fine. I put it together and tried it again. Turned over fine but right as I let OFF the key is when it fired. Tried it a few more times same thing, turn over all day long pressing key all the way down but will only fire right as I'm am letting off. I replaced the ignition switch on the base of the column, same thing. I adjusted up and down same thing. I put in a new key switch in this evening hoping that would fix it but still the same thing. What else could it be? Sorry this is so long but I am stumped and I have fixed everything I thought it could be what am I missing? Thanks in advance.

04-04-2010, 11:51 PM	#7
westofb I really hate wet sanding! Join Date: Dec 2008 Location: Brookfield, MO Posts: 601	Re: truck fires when letting off the key? still sounds like igintion switch prob to me. did you install a brand new one, or another used one? By what you are saying, you are not getting power to the distributor in the start position, only in the run position. Someone mentioned neutral safety switch, I doubt that is the problem, that should only prevent the the engine from cranking. Have you checked all the fuses in the under dash fuse panel? I cant remember for sure off top of my head, but there may be a blown fuse, one that is only hot in the when the key is in the start postion. Good luck getting it going. __________________ Jeff, 68 C-10 75 C-20, now a C-10! 10 F-150

04-05-2010, 01:25 AM	#8
rfmaster Registered User Join Date: Oct 2003 Location: OC CA Posts: 1,374	Re: truck fires when letting off the key? Based on your description it appears that ignition coil is not getting +12V during cranking, but does when ignition key is in RUN position. As always, assume nothing - question everything - get your DVM or a test light and verify that coil receives +12 V when ignition key is in run and crank positions. Worn ignition key contacts are usual suspects. //RF __________________ "The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17)

04-05-2010, 03:07 AM	#9
PRattenbury Senior Member Join Date: Feb 2010 Location: Maumelle, AR Posts: 478	Re: truck fires when letting off the key? Starter motor wiring. Check the solenoid wiring on the run and start tabs.

04-12-2010, 07:34 PM	#10
jimmybeus Registered User Join Date: Nov 2008 Location: La Barge Wyoming Posts: 63	Re: truck fires when letting off the key? Well I got it fixed. The coil was not getting power while it was cranking. Found a cut wire by the fuse box that had power while key was on and while cranking so I tapped on that one and it works great. Thanks for the ideas.



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