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Home » Public Forums » GMCnet » GMC MOTORHOME POWER LOSS PROBLEM (STRICKEN FOR YEARS WITH POWER LOSS-ASKING FOR HELP)
GMC MOTORHOME POWER LOSS PROBLEM [message #292162] Tue, 15 December 2015 10:35 Go to previous message
Gatsbys' Cruiser is currently offline  Gatsbys' Cruiser   United States
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Registered: August 2014
Location: Illinois
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*** First, let me apologize for bringing this to the table. I do not like to bring my problems out to anyone else, preferring to find a solution myself. I do not like to bother anyone else. However, this problem has lasted almost if not 10 years, has restricted any kind of travel and is becoming a money pit. If any of you could come up with a solution I would owe you so much, I can never repay you. So, here is my delema ***


Hello folks. I have a bad problem that has plaqued the GMC for years now and my mechanic and I are running out of ideas. Here is the history...

*** When I bought the GMC, I headed home and experienced a power loss. This occurred miles down the road and started at 65 but as the miles added up, the top speed slowly began to go down. After having the distributor replaced by a GMC dealer ( I did not know at the time but it was NOT the Motorhome type, but it turned out it didn't matter because there was NO VACUUM lines working thanks to the PO cutting them off. Only the brakes had vaccuum. I was able to drive with no problems other than a gas leak at fill up. It was the fuel lines.

***After having the fuel tanks inspected and fuel lines replaced, it experienced a power loss. At first could'nt get above 35mph. It was determined that the carborator had a problem but the 3 rebuilt carbs that were put on, didn't make any improvement. The distributor was changed out with a used one from a GMC motorhome and the used Carb from a GMC motorhome and it seemed to run ok.

On the way home everything seemed ok until I refueled. Upon setting off from the gas station the power loss occurred at 55. We pulled over and tried to figure out what was going on but couldn't find anything. We sat about 30 minutes, then started back on the road. The power loss problem did not come back until we refueled again. After stopping for 30 minutes, we headed home and no problem again????? This would happen all the way home.

***I took it to the mechanic and he made some adjustments to the carborator and the problem seemed to be gone. He had found that the vacuum lines were not connected so he put vacuum back to the distributor.

***Went on a 6 hour trip to some friends place where I stayed a week. I did not, that I can determine, experience any problem on the way to thier cabin. After being there a week, Time came to go home and she started up ok, stopped at a gas station to fill up and as we started down the road, the power loss was back at 55 mph. The problem would be there all the way home but this time my top speed would decrease until I was trying to get as fast as i could go to be able to "coast" over the hills and bridges. I was able to limp home.

***It was determined that the carborator needed to be over hauled so that was replaced with rebuilt one and the fuel pump was replaced and a in line fuel filter was added. The problem seemed to be gone. I did take a couple of trips that seemed to be without a problem but the problem returned on a return trip.
***It was taken back for carborator adjustments again, inspection never turned anything up unusual visually. Timing was checked, plugs, wires, coil.
***Winter was here and the GMC was stored. I tried to start the GMC occasionally since she did IDLE very nicely. Come Spring, the GMC was to be at the mechanics to try to find the problem again. Over the coarse of Winter, The GMC was now becoming hard to start, I suspected The fuel was draining back to the tank and the fuel pump struggled to bring fuel back up to the carborator. It became harder to start until she wouldn't start at all. The problem was fuel and I tried different ways to get fuel to the carborator, nothing worked. I ended up using an external gas can and electric fuel pump to get her to start. With this crazy configuration I drove it to the mechanic again.

***This was going to be the final repair. Everything was checked, wires, distributor, timing. We found cracks in the manifold so that was replaced and the cross overs blocked. Replaced the fuel solenoids and added an electric fuel pump to purge after sitting a long while. The fuel filters were replaced, But the carborator was not responding to any adjustments. There was no warrentee being honored on the carb so I told the mechanic to open it up and inspect it.

What he found would be shocking. The carborator was full of RUST. The rust had infiltrated everything and was determined to be unrepairable. The filter at the carborator was plugged solid with rust. We cut open the fuel filter back by the fuel solenoids and it was CLEAN. So where was the rust coming from? We cut open the fuel pump and it was destroyed by rust. The interior was rusted out.

The fuel pump was replaced, the fuel lines forward the fuel pump replaced and I found a GMC motorhome carb that was rebuilt, had been used and stored on a shelf for a year. I purchased the carborator and it was installed.

We started the GMC up, she idles like a new car. No vibration, smooth as silk. We took it for a test run, got it up to 65 mph but had a hesitation. We found that the right front brake was stuck braking and thought that might be the problem. In the Spring, The brakes were gone through and we ran her for a test again. This time top speed was 45 mph.

We've tried to get the adjustments on the carb but the power loss occurrs at different speeds from 35mph to 45mph. Cant get her above 45mph.

We are fast losing faith and the mechanic is scratching his head. Nothing seems to be helping. Do note that when she idles she runs like a fine tuned machine.

***We have tested for fuel volume and seems to be ok. Our next step will be to run it off of an external tank to see if the problem clears up. But being we were up to 60 before the problem occurred last year, this seems to be over kill. But we have replaced everything I can think of and the problem persists.

We are actually talking about having the carborator rebuilt professionally in the Spring, I don't know if there are any other options.

I am very near taking her to a GMC dealer next year and see if they can figure it out. As Winter is upon us I can only try a couple of simple things before putting her in storge over Winter.

If anyone can shed any, and I mean ANY idea on what is going on???? I would be very grateful.

I appreciate any time or help you can shed on this problem. I am at wits end after all these years.
Thank you for reading
slc
slawrence111 (at) yahoo (dot) com
847 (dash) 662 (dash) 6707

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