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| [GMCnet] Short trip report [message #98324] |
Fri, 03 September 2010 06:59  |
Gary Casey
Messages: 448
Registered: September 2009
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Maybe the title should say "report of a short trip" not "short trip report".
After a year of various repairs and refurbishment it was time to get it on the
road, hopefully in time to tour the high country of Colorado. We drove it home
to Denver from Minneapolis with only 3 incidents: Broken alternator belt,
inoperative fuel tank solenoid valve (the only way that was detected was by
running low on fuel - my fault), and wiring short at the battery with the
accompanying minor fire. Did a valve job with new timing chain and distributor,
new ball joints on one side, 2 new wheels and tires (now I only need 2 more
Alcoa's). First trip lasted 2 miles when I discovered fairly massive
transmission leaks. Found all the bolts loose between the transmission and
final drive plus a loose cooler line fitting. Next trip got us 10 miles away,
when something happened to the fuel supply - looked like a stuck float. Took
carb apart, cleaned it and found a bad check valve in the filter. Then it ran
perfect. Yesterday's camping trip got us 40 miles away when. We knew we were
almost out of gas(nearest gas station is 20 miles from home), but that wasn't it
- the ignition wasn't getting power. Jumped it from the fuse box. Don't even
have to go outside to work on these things - aint it cool? Decided to keep
going, but then it started to have vapor lock symptoms. If we stopped to idle
for a bit it would have trouble getting up to speed, but after coaxing it for a
bit everything was okay. So we decided not to go up the grade west of Colorado
Springs and head back home. Next time I'm looking forward to getting 200 miles
from home (each trip is 4 times longer than the last!). The weather was in the
70's and all elevations were between 6000 and 7000 feet.
Questions:
Having trouble finding the open in the ignition feed. Ignition power goes
through the firewall connection, but how does it get from there to the
distributor? The coach was converted to HEI and I assume the resistance wire
was eliminated, but what was put in its place? The "R" terminal on the starter
still feeds power to the ignition (that's how I tracked down the problem
originally), but where does that wire connect into the system? I'm having
trouble finding it.
The fuel system, with a new tank solenoid valve and new fuel pump, acts like it
has a pinched fuel line. But it acts the same on either tank. The PO said he
replaced all the fuel tank lines, and they look relatively new. Even under
"good" conditions it has trouble running full throttle above 3000 rpm - acts
like fuel starvation. The idea someone had of throwing away the mechanical fuel
pump and selector valve (both new - ouch) and installing two electric pumps, one
from each tank, sounds better all the time. Obviously, when new it would run
strong up to the shift points, right......?
When filling the tank, I get a leak when it is topped off. The return line to
the filler neck is hard as a rock - probably leaking someplace, but it seems to
be really hard to get at to change. Right?
The OEM oil pressure gauge shows that the oil pressure is always varying as a
function of engine speed and temperature and at 2500 rpm when hot it is in the
middle of the range. Lower rpm will show it dropping pretty much proportional
to engine speed. I would expect oil pressure to be held reasonably constant by
the pressure regulator. Is what I'm seeing about normal for a 150,000 mile
engine? (20W-50 oil)
The holding tank leaks at the outlet valve fitting - I assume this is a simple
repair....?
Finally, one of the outer CV boot clamps came off. I put on a new one (a pricy
$2.50 from Autozone - for 2) and it slipped off the first time I drove it. The
boot looks good, so I don't want to replace the boot or axle if possible. One
thing that surprised me is that the boot doesn't have a lip to retain the clamp
- it can just slip off. And it doesn't have an internal land as wide as the
groove in the joint, so it is easy for it to slide back and forth. Is there a
"magic bullet" for this problem?
And finally, the real problem - my wife is losing faith in "Bus" (it's yellow),
and is about ready to give it away. Heeeelp.....
Gary Casey
'73 23, Colorado
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| Re: [GMCnet] Short trip report [message #98344 is a reply to message #98324] |
Fri, 03 September 2010 10:17  |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Gary,
In answer to a few of your questions...
On the fuel overflow return line, it is 1/2 inch diameter and connects behind the drivers side panel, then runs down about 3 ft and attaches to a steel line going to the rear.
The oil pressure gauge normally fluctuates with temperature and rpm and yours sounds about right.
If the only fuel filter is in the carb and it is clean, you might be suffering from debris/trash in the socks over the fuel pick ups in the tanks. Some report using compressed air back through the pick up line to improve fuel pick up. If you do this, you might want to add an inline fuel filter.
Leaking black tank may be the seal of the valve to the tank, cracks in the fitting welded to the tank or bad seals around the slide valve. OEM style replacement Therford valves are $55-75 and are not difficult to replace.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=34279&title=0084&cat=4620
Good luck.
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Short trip report [message #98347 is a reply to message #98324] |
Fri, 03 September 2010 10:34 |
g.winger
Messages: 792
Registered: February 2008
Location: Warrenton,Missouri
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I don,t know for sure, but,,, on point dist. one terminal on the starter sol. was to give full voltage (ie. no balast resistor)to the ciol whle cranking for a hotter spark. I'm sure some one else will pipe in and confirm,,,,unless i'm mistaken.
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| Re: [GMCnet] Short trip report [message #98354 is a reply to message #98324] |
Fri, 03 September 2010 11:51 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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John,
Sorry, was trying (unsuccessfully) to keep the report short. The "R" terminal
is only used by early breaker-point style ignitions (pre '75?). When the
starter solenoid engaged, it connected the ignition directly to the battery,
bypassing the resistor wire that normally fed the ignition, making for a hotter
spark during crank. Mine was converted to HEI so there was no need for the
wire, but instead the HEI is powered directly without the resistor wire. How
the PO did that is uncertain to me - hard to track it down. The wire from the
ignition goes down the front of the engine and there I kind of lose it (unless I
go in through the wheel well. I might decide to run a new wire.
Gary
Gary Casey wrote on Fri, 03 September 2010 07:59
> Maybe the title should say "report of a short trip" not "short trip report".
>
>
> Questions:
> Having trouble finding the open in the ignition feed. Ignition power goes
> through the firewall connection, but how does it get from there to the
> distributor? The coach was converted to HEI and I assume the resistance wire
> was eliminated, but what was put in its place? The "R" terminal on the
>starter
> still feeds power to the ignition (that's how I tracked down the problem
> originally), but where does that wire connect into the system? I'm having
> trouble finding it.
Is there supposed to be a wire connected to the "R" terminal on the starter
solenoid? Ours has no wire connected there - what is that terminal for?
John
--
John Shotwell
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| Re: [GMCnet] Short trip report [message #98389 is a reply to message #98354] |
Fri, 03 September 2010 16:47 |
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| Gary Casey wrote on Fri, 03 September 2010 11:51 |
The wire from the
ignition goes down the front of the engine and there I kind of lose it (unless I
go in through the wheel well. I might decide to run a new wire.
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What color is that wire?
Little Yimmy - W9VUA
75 PB - F260206
Twin Cities, MN
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| Re: [GMCnet] Short trip report [message #98428 is a reply to message #98324] |
Fri, 03 September 2010 20:42 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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Senior Member |
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Gary,
I don't remember much of the specifics, but I was a dealer tech back when HEI came out with 1975 GM models. I remember the trainers saying it was pretty sensitive to voltage (part of the reason it should have at least a 12 gauge wire supplying it). I think they said if it got much below 10 volts you were probably walking.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: [GMCnet] Short trip report [message #98440 is a reply to message #98420] |
Fri, 03 September 2010 22:06 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Gary Casey wrote on Fri, 03 September 2010 21:01 |
I think I just solved the mystery. The PO apparently powered the HEI conversion from the original resistor wire, which I found in the harness, but assumed it was dead. He spliced it to the wire from the starter "R" terminal. Dumb move in more than one way. First, the nichrome wire is pretty much impossible to solder and it fell apart, maybe as a result of me fussing with the harness when I had the engine apart. And secondly, how well will the HEI work when powered through the resistor? I'm sure the spark energy was less than it could have been and was the timing reliable? I found the front end of the wire at the bulkhead connector and I'm going to replace the whole thing - and remove the starter wire from the harness. The PO talked a good story, spending some time talking about the race cars he built.... and I listened. Dumb me. Now to dive into the fuel starvation issue.
Gary Casey
Learning every day
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Gary,
We did some catalyst testing for GM. The plan was to induce misfire by reducing the voltage to the HEI module. The plan didn't work very well. The timing pretty much stayed on, but went misfire started it was very serious and not the occasional miss that could be ignored.
As you are probably running plugs at 0.035, you may not even be able to detect an improvement in fuel rate. The case got worse with increasing manifold pressure (more throttle), so you may notice a change there.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Short trip report [message #98467 is a reply to message #98324] |
Sat, 04 September 2010 06:06 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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The wire is black with lettering on it, "Resistance wire. Do not cut." It
comes out of the main connector block and goes non stop to the distributor.
Gary
Gary Casey wrote on Fri, 03 September 2010 11:51
> The wire from the
> ignition goes down the front of the engine and there I kind of lose it
(unless
>I
> go in through the wheel well. I might decide to run a new wire.
What color is that wire?
--
Little Yimmy - KC?SQS
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