| [GMCnet] Poor Mileage solved [message #324615] |
Wed, 04 October 2017 19:56  |
emerystora
Messages: 4442
Registered: January 2004
Karma:
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Senior Member |
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I put in a rebuilt 455 engine last January. I have about 6000 miles on it and have only used 1/2 quart of oil and it is running great.
However after installing it I was only getting about 7 miles per gallon.
Upon going and returning from the GMCMI Convention at Elkhart I was getting closer to 6 miles per gallon.
Yesterday while on I-80 in Iowa my engine stalled so I pulled over to the side of the highway.
I knew that I had fuel but it would not start so I lifted the engine cover and checked for spark.
There was none. I took off the distributor cap and it looked good and the rotor looked good so I replaced the distributor module.
It still wouldn’t start. I also carry a spare coil with me so I took off the coil cover and found that the coil was so hot that I could not touch it.
I got gloves and replaced it and reassembled the distributor and the engine started right up.
For the next two tanks of fuel I have gotten close to 9 miles per gallon even towing my Tracker and going about 70 mph on the Interstate. The motorhome also accelerated better and idled faster.
Apparently I had a dying coil and it likely was not firing the plugs all the time which gave me the poor mileage. Funny that the engine seemed to run smoothly though and I couldn’t detect a miss.
I carry spares for the distributor including cap, rotor, module, coil and pole piece (coil beneath the module). I have used all of the spare parts except the coil in the 36 years that I have had the GMC but I am sure glad that I had a coil with me. It is usually the module that goes bad but my rotor, cap, and pole piece have also failed in the past while on a trip.
I would have been laid up for many hours on this trip and probably would have had to be towed for over 100 miles if I had not carried the spare parts and knew how to install them.
Emery Stora
77 Kingsley
Frederick, CO
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