No Power Uphills

I have a 1990 Sierra with a fuel injected 350 which first started losing power up hills and now after about thirty seconds underload on flats.
If I turn the engine off and restart immediately it runs like new but only for half a minute. I thought it was the fuel pump but now am not so sure. Any Ideas?

spark plugs, wires, full tuneup if it hasent had one recently.

I have a 1990 Sierra with a fuel injected 350 which first started losing power up hills and now after about thirty seconds underload on flats.
If I turn the engine off and restart immediately it runs like new but only for half a minute. I thought it was the fuel pump but now am not so sure. Any Ideas?



I have been trying to fix a no power problem for about 2 years. I took it to three small time local garages that did the tune up thing, one told me that the timing was way retarded. It got so bad that it became very difficult to drive. It would not pull me at 65 mph down the highway unless I shifted out of overdrive. I finally broke down and took it to a GM dealer. They said that it was a common problem for the early 1990 GM 5.7 liter (350 cubic inch) engines to develop a loose reluctor on the distributor shaft. They replaced the distributor shaft and I now have a truck that runs like new. Oh did I say that I have a 1993 GMC Silverado, Hmmmmmmm not awake it should have read 1993 GMC Sierra.

Kim
Saskatchewan, Canada

I have been trying to fix a no power problem for about 2 years. I took it to three small time local garages that did the tune up thing, one told me that the timing was way retarded. It got so bad that it became very difficult to drive. It would not pull me at 65 mph down the highway unless I shifted out of overdrive. I finally broke down and took it to a GM dealer. They said that it was a common problem for the early 1990 GM 5.7 liter (350 cubic inch) engines to develop a loose reluctor on the distributor shaft. They replaced the distributor shaft and I now have a truck that runs like new. Oh did I say that I have a 1993 GMC silverado.

Kim
Saskatchewan, Canada

Thankyou I'll give this a try.

spark plugs, wires, full tuneup if it hasent had one recently.

Done all the obvious things.

I have a 1990 Sierra with a fuel injected 350 which first started losing power up hills and now after about thirty seconds underload on flats.
If I turn the engine off and restart immediately it runs like new but only for half a minute. I thought it was the fuel pump but now am not so sure. Any Ideas?


I found it rather difficult to check fuel pump pressure without special fittings. I have an old low pressure gauge so I hooked it up to my old filter. I used a sharp scratch awl and punched a hole in the inlet end of the fuel filter. I inserted and the soldered a ¼ inch length of copper tubing into the hole. I had a 6 foot length of ¼ inch snowmobile gas line that I used to connect the filter tube to my low pressure gauge. I routed the hose over the frame and up into the cab. When I started the truck up and took it for a drive, the pressure remained at about 22 lbs. per inch. The pressure held constant at highway speeds. If anyone tries this use a soldering iron, not an open flame when soldering. Work in a well ventilated area and be prepared for a small fire it the old fuel filter decides to burn. Oh ya don’t try soldering the ¼ inch tube with the filter still installed in the truck. I did my soldering outside on a sawhorse, wore welding gloves and a face shield.
Kim