problem starting 76 GMC - The 1947 - Present Chevrolet & GMC Truck Message Board Network

screwballl · 03-23-2005, 12:54 AM

ok this is a very unusual problem, it only seems to happen mostly when it is very high humidity or raining within 4 hours of needing to start it...
like this morning, it started fine but 2 blocks down the road it just died and wouldnt start back up... it seems somewhat at random but the moisture is the only thing i can think of...
what i've done:
replaced carb (needed done anyways Rochester was shot) has Edelbrock 600cfm elec choke remanu from Edelbrock themselves (9104??). This was done about 6 months ago.
replaced spark plugs, wires, distributor cap, rotor, HEI, module in dist within 3-4 months ago.

i can smell gas when i try to start it but its acting like its not getting spark. most everything spark related (that i am aware of) has been replaced. the only thing i can think of might be the vacuum advance or fuel pump? or maybe voltage regulator? i am not a mechanic so i can't diagnose these things but i can replace most anything on this truck.
I am not looking to spend $200 on a HEI or get $60 spark plugs. it is an old tired engine that still has miles left on it but i am not ready to put serious money into it (not liek i have a choice, the wife won't let me).
It is a stock 350, the VIN says this truck originally had a 6 in it but i am guessing someone put in this GM Goodwrench 350 sometime in the 80s or maybe very early 90s. When it runs, it runs excellent but this odd problem keeps happening at the worst of times like this morning on my way to work in the rain.

Brad_Olson · 03-23-2005, 09:18 AM

Just a Wednesday morning WAG, but when you installed the new HEI cap and the plug wires did you give the cap lip and the boots a thin film of grease to help act as a moisture barrier? This is my first thought but it seems odd that the engine runs and then dies instead of simply refusing to start.

Brad

screwballl · 03-23-2005, 09:16 PM

yes i did... sometimes it wont start at all for 2 days, sometimes i won't have a problem for several weeks... it seems very sporadic
i tried it finally tonight after 2 days and after banging on the fuel pump, dist cap and vacuum advance it started albeit running rich and smoking a little from burning off the extra gas... ran it around town for 15-20 minutes and the smoking cleared up and seemed to do fine...
so this is very confusing

badone07 · 03-23-2005, 10:42 PM

Had the exact samething happen with a Firebird only on rainy or humid days. It was the ignition module. The gas smell and floading was caused by no spark....did you check for spark when it acts up?

screwballl · 03-27-2005, 03:13 AM

as I am the only one that knows a hint of whats going on, theres no one in my house to help with that...
I've been looking around, may have found a 99 Z71 for decent price locally... probly just sit the 76 in the side yard and do some small restoration like remove rust and mess a bit with the engine then sell for $4K or whatever seems decent...

03-23-2005, 12:54 AM	#1
screwballl Tonawanda 454 Join Date: Mar 2004 Location: Liquid Sunshine State Posts: 2,754	problem starting 76 GMC ok this is a very unusual problem, it only seems to happen mostly when it is very high humidity or raining within 4 hours of needing to start it... like this morning, it started fine but 2 blocks down the road it just died and wouldnt start back up... it seems somewhat at random but the moisture is the only thing i can think of... what i've done: replaced carb (needed done anyways Rochester was shot) has Edelbrock 600cfm elec choke remanu from Edelbrock themselves (9104??). This was done about 6 months ago. replaced spark plugs, wires, distributor cap, rotor, HEI, module in dist within 3-4 months ago. i can smell gas when i try to start it but its acting like its not getting spark. most everything spark related (that i am aware of) has been replaced. the only thing i can think of might be the vacuum advance or fuel pump? or maybe voltage regulator? i am not a mechanic so i can't diagnose these things but i can replace most anything on this truck. I am not looking to spend $200 on a HEI or get $60 spark plugs. it is an old tired engine that still has miles left on it but i am not ready to put serious money into it (not liek i have a choice, the wife won't let me). It is a stock 350, the VIN says this truck originally had a 6 in it but i am guessing someone put in this GM Goodwrench 350 sometime in the 80s or maybe very early 90s. When it runs, it runs excellent but this odd problem keeps happening at the worst of times like this morning on my way to work in the rain. __________________ 91 Chevy Suburban Tonawanda 454 R2500 - SOLD!!! 04 Dodge Durango 5.7L Hemi 2WD, 24K miles (as of July 2011) In the past 30 years about 90% of Fords are still on the road, the other 10% made it home. -------------------

03-23-2005, 09:16 PM	#3
screwballl Tonawanda 454 Join Date: Mar 2004 Location: Liquid Sunshine State Posts: 2,754	yes i did... sometimes it wont start at all for 2 days, sometimes i won't have a problem for several weeks... it seems very sporadic i tried it finally tonight after 2 days and after banging on the fuel pump, dist cap and vacuum advance it started albeit running rich and smoking a little from burning off the extra gas... ran it around town for 15-20 minutes and the smoking cleared up and seemed to do fine... so this is very confusing __________________ 91 Chevy Suburban Tonawanda 454 R2500 - SOLD!!! 04 Dodge Durango 5.7L Hemi 2WD, 24K miles (as of July 2011) In the past 30 years about 90% of Fords are still on the road, the other 10% made it home. -------------------

03-23-2005, 10:42 PM	#4
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	Had the exact samething happen with a Firebird only on rainy or humid days. It was the ignition module. The gas smell and floading was caused by no spark....did you check for spark when it acts up? __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car)

03-27-2005, 03:13 AM	#5
screwballl Tonawanda 454 Join Date: Mar 2004 Location: Liquid Sunshine State Posts: 2,754	as I am the only one that knows a hint of whats going on, theres no one in my house to help with that... I've been looking around, may have found a 99 Z71 for decent price locally... probly just sit the 76 in the side yard and do some small restoration like remove rust and mess a bit with the engine then sell for $4K or whatever seems decent... __________________ 91 Chevy Suburban Tonawanda 454 R2500 - SOLD!!! 04 Dodge Durango 5.7L Hemi 2WD, 24K miles (as of July 2011) In the past 30 years about 90% of Fords are still on the road, the other 10% made it home. -------------------

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03-23-2005, 09:18 AM	#2
Brad_Olson Active Member Join Date: Mar 2005 Location: Stoughton, WI Posts: 187	Just a Wednesday morning WAG, but when you installed the new HEI cap and the plug wires did you give the cap lip and the boots a thin film of grease to help act as a moisture barrier? This is my first thought but it seems odd that the engine runs and then dies instead of simply refusing to start. Brad



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