Home » Public Forums » GMCnet » Help for engine
| Help for engine [message #179927] |
Sun, 12 August 2012 08:35  |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Hi and thanks in advance for any help. Planning on hitting the road on Thursday, well, I WAS planning, for a weekend at Mt. Shasta then dropping my 76 PB off at Applied in Fremont to invest a few $$$ in some needed upgrades.
But this morning on my weekly drive it didn't. Precursor was last week when I heard a couple of Pphhh sounds, short, quick sounds, almost a pop, that in another engine long ago was backfiring through the carburetor due to what I don't remember, intake manifold gasket? Anyway, this morning I drove her down a gentle hill to get morning coffee and decided to take her back home instead of my usual 1/2 hr drive on Sunday, and she almost wouldn't make it back up the very slight hill. In all running very rough, though started quickly no problem (Howell EFI). Supposedly about 15k mi on "engine rebuild" by PO. The only work I've done other than spark plugs 1000 mi ago is replacing exhaust header gaskets (~2000 mi ago), but this new sound is totally different than what I was hearing when they were leaking.
In a bit of a panic. Hope someone can give me some ideas based on totally limited information. Thanks.
Jay Rabe
76 PB
Portland, OR
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| Re: Help for engine [message #179928 is a reply to message #179927] |
Sun, 12 August 2012 08:38  |
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Sounds like you may need a new Ignition Module (and always carry a spare). It could also be the coil (mine did the same thing when it went bad)
Then check the plugs for the correct gap. The original requirement is too wide and causes ignition parts to fail.
Good Luck
John Ruff
| jayrabe wrote on Sun, 12 August 2012 06:35 |
In a bit of a panic. Hope someone can give me some ideas based on totally limited information. Thanks.
Jay Rabe
76 PB
Portland, OR
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John Ruff
Chandler, AZ
1975 Eleganza
WA3RIG
If I use ZDDP in a new car - will the tappets go flat?
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| Re: [GMCnet] Help for engine [message #179936 is a reply to message #179927] |
Sun, 12 August 2012 09:14 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Jay,
The sound isn't familiar (few are, with my 1/2 effective single ear), but
if you suspect a vacuum leak, try squirting WD-40 or some other
butane-propelled lubricant at the right rear of the throttle body where it
bolts to the manifold. If the engine speed changes with the squirting,
there's a leak there. Reason being, that's where the Holley TB doesn't
match the manifold and RTV is used to "prevent" vacuum leaks.
If there proves to be a leak there, you can buy a SS shim to seal that area
more effectively. It's made by our Bill Brown's son Jim. I'll provide
more info if needed.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Sun, Aug 12, 2012 at 9:35 AM, Jay Rabe wrote:
>
> ... Precursor was last week when I heard a couple of Pphhh sounds, short,
> quick sounds, almost a pop, that in another engine long ago was backfiring
> through the carburetor due to what I don't remember, intake manifold
> gasket?...
>
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www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Help for engine [message #179938 is a reply to message #179936] |
Sun, 12 August 2012 09:58 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Senior Member |
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I'll be able to check that out late tonight. Thanks for the tip. In addition to the pop/fluff noise, the other major symptom is that it's running very very rough, rattling the whole exhaust system, and up until last week it ran nice and smooth.
One other recent thing: Friday I had a fuel leak at a hose fitting on top of the engine where PO had joined a 5/16 fuel line to a 3/8 fuel line and just used a piece of metal line and tightened the hose clamp down a lot on the too-big 3/8 line. Anyway, got a proper reducer/splicer, but in the process I did remove/check/reinstall the barb fitting from the carburetor, but it took a bit of torque to get it off, so maybe I disturbed the seal to the manifold.
Anyway, thanks Ken. Do so hope you're right and some high-temp RTV will get me to CA and I'll just add a shim to my list for Nick & Jim.
Jay
76 PB
Portland, OR
> From: hend4800@bellsouth.net
> Date: Sun, 12 Aug 2012 10:14:06 -0400
>
> ...
> if you suspect a vacuum leak, try squirting WD-40 or some other
> butane-propelled lubricant at the right rear of the throttle body where it
> bolts to the manifold. If the engine speed changes with the squirting,
> there's a leak there. Reason being, that's where the Holley TB doesn't
> match the manifold and RTV is used to "prevent" vacuum leaks.
>
> If there proves to be a leak there, you can buy a SS shim to seal that area
> more effectively. It's made by our Bill Brown's son Jim. I'll provide
> more info if needed.
>
> Ken H.
> Americus, GA
> '76 X-Birchaven w/Cad500/Howell EFI+ & EBL
> www.gmcwipersetc.com
>
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| Re: [GMCnet] Help for engine [message #179977 is a reply to message #179975] |
Sun, 12 August 2012 16:34 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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This is a long shot, but I would be checking the spark plugs. It is possible that one has come loose or out altogether. Also, as Larry suggested, check vacuum lines and plugs on the engine.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Help for engine [message #180003 is a reply to message #179977] |
Sun, 12 August 2012 19:42 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Two things make the engine go, Fuel and spark. If it is backfiring
out the exhaust then the first place I would look is the ignition
system and would change the module first then check the rest of the
ignition system. The module will fail in many wondrous ways. If the
engine is popping back thru the throttle body then I would be looking
at my fuel pressure and then my fuel filters. Lets get the basics out
of the way first before we move on. It ran well before so most likely
it is something basic.
JR Wright
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GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Help for engine [message #180062 is a reply to message #180003] |
Mon, 13 August 2012 10:19 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Alarm goes off at 0400, home from work about 1900. Not much time left for troubleshooting until "weekend" starts on Thu.
However I started her up last night and sprayed WD40 where I thought I was supposed to, but no change in engine speed. That said, it didn't pop or backfire either, though I didn't try to drive it. I checked the vac hoses and all were intact, as were spark plug wires.
Tonight I'll check the vac hose to the modulator DP suggested and check compression and try to drive it. And also I'll dig through box of spares from PO as I think there may be an ign module there.
If I replace the ign module, from the manual it looks pretty easy, 4 wires total in two connectors, but it wants "special silicone grease" presumably heat sink compound. I see from NAPA site they have little pill capsules of such. Is that what I want to use?
Thanks,
Jay Rabe
76 PB
Portland, OR
> From: powerjon@chartermi.net
> To: gmclist@temp.gmcnet.org
> Date: Sun, 12 Aug 2012 20:42:21 -0400
> Subject: Re: [GMCnet] Help for engine
>
> Two things make the engine go, Fuel and spark. If it is backfiring
> out the exhaust then the first place I would look is the ignition
> system and would change the module first then check the rest of the
> ignition system. The module will fail in many wondrous ways. If the
> engine is popping back thru the throttle body then I would be looking
> at my fuel pressure and then my fuel filters. Lets get the basics out
> of the way first before we move on. It ran well before so most likely
> it is something basic.
>
> JR Wright
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Help for engine [message #180072 is a reply to message #180062] |
Mon, 13 August 2012 10:58 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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You can find the "special grease", more commonly called dielectric
grease at most autoparts stores. Here are some examples:
http://tinyurl.com/cqwa6kv
or
http://tinyurl.com/9hdqhpu
There are several more expensive greases which work well also:
http://www.radioshack.com/product/index.jsp?productId=2102858
and
http://www.radioshack.com/product/index.jsp?productId=3964625
The last one is probably the best for thermconductivity.
JR Wright
GMC Great Laker MHC
GMC Eastern States
GMCMHI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan
On Aug 13, 2012, at 11:19 AM, Jay Rabe wrote:
>
> Alarm goes off at 0400, home from work about 1900. Not much time
> left for troubleshooting until "weekend" starts on Thu.
>
> However I started her up last night and sprayed WD40 where I thought
> I was supposed to, but no change in engine speed. That said, it
> didn't pop or backfire either, though I didn't try to drive it. I
> checked the vac hoses and all were intact, as were spark plug wires.
>
> Tonight I'll check the vac hose to the modulator DP suggested and
> check compression and try to drive it. And also I'll dig through box
> of spares from PO as I think there may be an ign module there.
> If I replace the ign module, from the manual it looks pretty easy, 4
> wires total in two connectors, but it wants "special silicone
> grease" presumably heat sink compound. I see from NAPA site they
> have little pill capsules of such. Is that what I want to use?
>
> Thanks,
>
> Jay Rabe
> 76 PB
> Portland, OR
>
>
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Help for engine [message #180181 is a reply to message #179927] |
Tue, 14 August 2012 08:02 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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Those little backfires often blow off plugs on unneeded vacuum fittings.
On Sun, Aug 12, 2012 at 6:35 AM, Jay Rabe <jayrabe@hotmail.com> wrote:
>
>
> Hi and thanks in advance for any help. Planning on hitting the road on
> Thursday, well, I WAS planning, for a weekend at Mt. Shasta then dropping
> my 76 PB off at Applied in Fremont to invest a few $$$ in some needed
> upgrades.
> But this morning on my weekly drive it didn't. Precursor was last week
> when I heard a couple of Pphhh sounds, short, quick sounds, almost a pop,
> that in another engine long ago was backfiring through the carburetor due
> to what I don't remember, intake manifold gasket? Anyway, this morning I
> drove her down a gentle hill to get morning coffee and decided to take her
> back home instead of my usual 1/2 hr drive on Sunday, and she almost
> wouldn't make it back up the very slight hill. In all running very rough,
> though started quickly no problem (Howell EFI). Supposedly about 15k mi on
> "engine rebuild" by PO. The only work I've done other than spark plugs 1000
> mi ago is replacing exhaust header gaskets (~2000 mi ago), but this new
> sound is totally different than what I was hearing when they were leaking.
>
> In a bit of a panic. Hope someone can give me some ideas based on totally
> limited information. Thanks.
>
> Jay Rabe
> 76 PB
> Portland, OR
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Fathom the hypocrisy of a nation where every citizen must prove they have
health insurance......but not everyone has to prove they're a citizen.
Steve Ferguson
Sierra Vista, AZ
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| Re: [GMCnet] Help for engine [message #180185 is a reply to message #180151] |
Tue, 14 August 2012 08:24 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Senior Member |
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Did search and don't have a spare ignition module. Per archives, I need AC Delco# D1906, GM PN 19180771. Is that correct? I believe I have an HEI distributor, with the coil built in to the top of it. Or is it better to just take it apart and look at the PN printed on my existing module?
Art & Doris noted that early indication of failure was being harder to start, though still running OK once started. Interesting that I'd noticed that in my coach. I drive it weekly, and the last two weeks I'd noticed it taking just a few seconds longer to start than it used to. Howell EFI in the past started almost immediately, but last two weeks it took maybe ~5 seconds longer. Not a lot, but significant and noticable. So I'm hopeful.
However, big-idiot-DOH discovery that my plug wires #3 & #6 were swapped. Crap. This is per the firing order diagram in the maint manual. Firing order will be the same regardless of distributor, right? Anyway, the only thing I can figure is that I screwed up when I changed the plugs 1500 mi ago. Plugs #3 & #6 are right next to each other on the distributor. Anyway, restored them to proper position and she started and idled OK last night, but it was already too far past my bedtime for a test drive. That's the plan for tonight, along with compression check. Is it possible that driving 1500mi with those plugs swapped could have burned a valve? Crap. Somebody slap me upside the head.
Jay Rabe
76 PB
Portland, OR
> To: gmclist@temp.gmcnet.org
> From: n9cv@comcast.net
> Date: Mon, 13 Aug 2012 20:33:55 -0500
> Subject: Re: [GMCnet] Help for engine
>
>
>
> Usually there is a little tube of it supplied with each new module.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
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| Re: Help for engine [message #180186 is a reply to message #179927] |
Tue, 14 August 2012 08:25 |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
Karma: 2
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Senior Member |
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I had a sudden case of "it runs like crap" just before I left on our current trip and it turned out that everything looked great but I had two bad vacuum hoses. The hose that goes to my HVAC stuff was so old and brittle that it broke and was barely holding together at a crack. It fell apart when I pulled on it. Later in the trip I found that the hose to the vacuum advance was in really bad condition where it had been laying on the intake crossover before it was blocked. I'd suggest examining the hoses carefully.
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
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| Re: [GMCnet] Help for engine [message #180188 is a reply to message #180185] |
Tue, 14 August 2012 08:30 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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I hope you used this one, some of the drawings in the maint. manual are
WRONG
http://gmcmotorhome.info/engine.html
gene
> However, big-idiot-DOH discovery that my plug wires #3 & #6 were swapped.
> Crap. This is per the firing order diagram in the maint manual. Firing
> order will be the same regardless of distributor, right? Anyway, the only
> thing I can figure is that I screwed up when I changed the plugs 1500 mi
> ago. Plugs #3 & #6 are right next to each other on the distributor. Anyway,
> restored them to proper position and she started and idled OK last night,
> but it was already too far past my bedtime for a test drive. That's the
> plan for tonight, along with compression check. Is it possible that driving
> 1500mi with those plugs swapped could have burned a valve? Crap. Somebody
> slap me upside the head.
>
> Jay Rabe
> 76 PB
> Portland, OR
>
>
>
>
>
> > To: gmclist@temp.gmcnet.org
> > From: n9cv@comcast.net
> > Date: Mon, 13 Aug 2012 20:33:55 -0500
> > Subject: Re: [GMCnet] Help for engine
> >
> >
> >
> > Usually there is a little tube of it supplied with each new module.
> > --
> > Ken Burton - N9KB
> > 76 Palm Beach
> > Hebron, Indiana
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Help for engine [message #180191 is a reply to message #180188] |
Tue, 14 August 2012 09:23 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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Maintenance Manual X-7625 (Supplement) contained
the corrected plug wiring diagram on Page 6Y-11,
Figure 4A.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
______________
*[ ]~~~[][ ][|\
*--OO--[]---O-*
> Date: Tue, 14 Aug 2012 06:30:28 -0700
> From: mr.erfisher@gmail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] Help for engine
>
> I hope you used this one, some of the drawings in the maint. manual are
> WRONG
>
> http://gmcmotorhome.info/engine.html
>
> gene
>
>
>
> > However, big-idiot-DOH discovery that my plug wires #3 & #6 were swapped.
> > Crap. This is per the firing order diagram in the maint manual. Firing
> > order will be the same regardless of distributor, right? Anyway, the only
> > thing I can figure is that I screwed up when I changed the plugs 1500 mi
> > ago. Plugs #3 & #6 are right next to each other on the distributor. Anyway,
> > restored them to proper position and she started and idled OK last night,
> > but it was already too far past my bedtime for a test drive. That's the
> > plan for tonight, along with compression check. Is it possible that driving
> > 1500mi with those plugs swapped could have burned a valve? Crap. Somebody
> > slap me upside the head.
> >
> > Jay Rabe
> > 76 PB
> > Portland, OR
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