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#1 |
Registered User
Join Date: Apr 2012
Location: Longmont, CO
Posts: 31
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1970 GMC probably a '72 engine, 350, Q jet, auto tranny. Just replaced the mechanical fuel pump. It still dies at 13 to 15 minutes, and it will have to cool down for at least an hour, then do it again. Any help would be appreciated.
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#2 |
Senior Member
![]() Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: engine dies in 15 minutes
What does it have to cool down for an hour? Will it not restart or?
__________________
68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi |
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#3 |
Registered User
Join Date: Apr 2012
Location: Longmont, CO
Posts: 31
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Re: engine dies in 15 minutes
It will turn over, but not fire. I've checked the gas cap, no vacuum in the tank. Just replaced the fuel pump, I can pull on the throttle and squirt fuel in the carb.
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#4 |
Senior Member
![]() Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: engine dies in 15 minutes
Do you have an HEI distributor? Almost sounds like the control module or something is bad and when it gets heated up, it's causing the truck to die. Another thought I had was the motor is running too rich and maybe flooding itself out? Are your spark plugs wet?
__________________
68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi |
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#5 |
Registered User
![]() Join Date: Dec 2015
Location: Holland Mi.
Posts: 302
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Re: engine dies in 15 minutes
Sounds like it could be a plugged fuel filter to me
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#6 |
Registered User
Join Date: Jan 2016
Location: Spokane WA
Posts: 106
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Re: engine dies in 15 minutes
Just had the same thing on my 67 GMC. It had the points distributor on it. After it ran for a while, 10-15 min it would die, then not start again, Wait an hour and it would fire up and again after 10-15 min it would do the same thing again. I went through EVERYTHING and finally put a new HEI distributor in it and it runs perfect now, no issues in 2 months.
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#7 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: engine dies in 15 minutes
The HEI modules can get flaky when hot - if you have a spare distributor, that'd be my guess. My first guess was tank venting, but you said no vacuum, so HEI it is!
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#8 |
Registered User
Join Date: Apr 2012
Location: Longmont, CO
Posts: 31
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Re: engine dies in 15 minutes
Thanks for the ideas, I'll get back to it next weekend.
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#9 |
Registered User
Join Date: Mar 2014
Location: Corvallis, OR
Posts: 712
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Re: engine dies in 15 minutes
Had a 1990 Suburban do the same thing. Just needed new cap/rotor, plugs, and wires. Ran perfect after that. Check that distributor too.
__________________
1972 GMC Jimmy Custom 4.8L (L20)/6L90E/NP205 1989 Chevy Suburban V2500 350/Turbo 400/4.11 gears 1996 Chevy Suburban K1500 350/4L60E |
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#10 |
Registered User
Join Date: Oct 2007
Location: Spanaway
Posts: 8,451
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Re: engine dies in 15 minutes
Something else, there is a short rubber hose below the tank, if its getting old and rotted it can collapse and restrict fuel flow, that includes any rubber line between the tank and pump, make sure its actual fuel line that is reinforced and not non reinforced rubber hose...
Check the filter like previously mentioned, try and back flow it with some air and see if there are any fine white chards of material in it, if there is that is the pickup sock deteriorating, time to replace the pickup screen.
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Mike. Swamp Rat build thread : http://67-72chevytrucks.com/vboard/s...d.php?t=595019 72 3/4T 4X4 4" BDS Lift 33" BFG's |
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#11 |
Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: engine dies in 15 minutes
+1 on ignition related components failing after heating up. Not too long ago, I purchased 64 Corvair and installed all new ignition parts. A mile or so down the road and it stop dead in its tracks. I decided to replace the points, condenser and ignition coil again...all was well the second time around. So, BOOB (Bad Out Of Box) parts are not uncommon.
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#12 |
Registered User
Join Date: Oct 2013
Location: Rt 66 Gallup, NM
Posts: 527
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Re: engine dies in 15 minutes
If it is the old points and condenser distributor, sounds like the coil is breaking down. To test it, remove it, then shake it, If it makes a sloshing noise replace it.
Could be the same for HEI.
__________________
2005 GMC K2500HD D/A 1993 GMC K1500 2011 Subaru Legacy. 2013 Subaru Outback 1970 C-10 2WD, SWB stepside, 292, TH350, PS, more rust than anything. God is my pilot. ![]() |
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#13 |
Registered User
Join Date: Apr 2012
Location: Longmont, CO
Posts: 31
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Re: engine dies in 15 minutes
Thanks for the ideas, I'll check them out.
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#14 |
Senior Member
![]() Join Date: Feb 2010
Location: Harrah, Washington
Posts: 323
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Re: engine dies in 15 minutes
Check that the fuel tank is venting. If you remove the gas cap and the problem goes away, then that's what it is.
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71 Blazer 4X4 (unmolested, all original (including paint) 74,000 mile barn find) 67 Camaro RS SS (unmolested, all original (including paint) 81,000 mile barn find) Keith Riel |
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#15 |
Registered User
Join Date: May 2012
Location: Farmington MO
Posts: 75
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Re: engine dies in 15 minutes
I would bet its the coil.
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#16 |
Registered User
Join Date: Mar 2009
Location: WARRENSBURG,MISSOURI,64093
Posts: 1,518
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Also, if you replaced the hei module recently and didn't use the dielectric grease,the module will fry to a crisp.... just sayin'
Ben ![]() |
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#17 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: engine dies in 15 minutes
He said no vacuum in the tank in his initial description.
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#18 |
Registered User
Join Date: Sep 2015
Location: central NJ
Posts: 102
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Re: engine dies in 15 minutes
fuel filter
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#19 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,240
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Re: engine dies in 15 minutes
Tank vent > fuel filter > distributor.................More likely distributor than fuel filter, but a filter is cheap and easy. If all that fails, I'd replace all fuel lines, including the vent line. If that fails, couldn't tell ya.
Don't know if that could be a fuel pump. Seems it would work or it doesn't.
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Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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#20 |
Registered User
Join Date: Mar 2009
Location: WARRENSBURG,MISSOURI,64093
Posts: 1,518
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Just something to check, but is there any fuel coming out the "Weep Hole" by chance? might want to make sure you have no fuel getting into your oil pan also....
Ben ![]() |
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#21 |
Registered User
Join Date: Apr 2012
Location: Longmont, CO
Posts: 31
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Re: engine dies in 15 minutes
Hello to anyone reading this, I put a new coil in today and doubled my run time. Now it will run for about 30 minutes. I bought a remote starter, but haven't figured how to hook it up, the directions are for a more modern vehicle. Can a part store test my module for me?
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#22 | |
Registered User
![]() Join Date: May 2014
Location: PA
Posts: 1,417
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Re: engine dies in 15 minutes
Quote:
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1967 C10, LWB, 250, Powerglide, PS, PB, 3/4 STATIC DROP |
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#23 |
Senior Member
![]() Join Date: Dec 2013
Location: Gods country East,Tn
Posts: 8,545
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Re: engine dies in 15 minutes
I still say it's a fuel issue , The dist ,coil,capacitor ,and anything else wouldn't continue to start multiple times and just run for 13-15 minutes ,It would have completely failed already .
Dirty fuel pick up in tank Fuel line between tank and hardline under cab collapsing / cracked Inline fuel filter Bronze fuel filter in carb it starts ,runs until crud in fuel line restricts flow .Won't restart ,wait an hour fuel flows back clearing line and restarts .Dies if 13-15 minutes . Why no pictures ? a good look at the condition of the rest of the engine/fuel lines and ignition could let someone give a further diagnosis .have you tried starting it once it dies using carb cleaner to see if it will fire even for a few seconds ? ![]() |
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#24 |
Registered User
![]() Join Date: Feb 2016
Location: Weatherford Texas
Posts: 306
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Re: engine dies in 15 minutes
You're either losing spark or you're losing fuel. Don't make it any more complex until you figure out which is the culprit.
When the thing dies, spray a spritz of carb spray or starter fluid down the carburetor. Does it try to start now ? If so, you have a fuel supply issue. If the spritz down the carb didnt cause it to try and start, pull a plug wire off and check for spark while cranking. |
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#25 |
Registered User
Join Date: May 2015
Location: Arlington, Texas
Posts: 10
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Re: engine dies in 15 minutes
When it dies look into the carb and see if the squirters are pumping fuel. Is the motor timed correctly? It could be getting hot due to poor timing and causing excessive heat that is vapor locking the fuel system. Are any fuel lines ran near the exhaust manifold?
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1972 Chevy C-10, BBC, Pro-Street SWB conversion |
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