My '87 GMC Suburban Sierra Classic with the TBI 350 and 700R4 has been a great truck. But last fall it began running rough and stalling out every time it rained. Since I live in Seattle, this was a big problem.
At first I didn't know what the problem was, so I took it to a shop where they seem to have a lot of customers with trucks with Chevy 350's. They ran some diagnostics on it and told me they couldn't find anything wrong, but from my description they suspected water in the fuel. I figured rainwater or condensation was somehow getting into the tank. The tank might have pinholes, or the rubber seal around the sending unit was bad, for example. Someone had cut a hole in the deck above the sending unit, and when I filled up the tank, if the carpet wasn't in, you could smell gasoline inside the cabin. Also, crap would fall onto the sending unit, which I figured couldn't be good for it.
To get it running again, I'd put a bottle of Heet (isopropyl alcohol) in the tank to solubilize the water in the gasoline, and a couple of hours later it'd be fine. Then it would rain again, and I'd put in another bottle of Heet. It got so I'd run out and put in a bottle of Heet while it was raining.
This got old, and I was buying a lot of Heet, so when the weather turned warm this summer I put in a new tank and new fuel lines. I replaced the filler hose, return hose, and sending unit with all new parts. However, the tank I removed didn't seem very old, like it had been replaced, and I couldn't find any holes in it. The sending unit seal looked good. The hose clamps seemed tight.
While the tank was out, I also welded up the hole in the deck above the sending unit.
I finished yesterday, and drove the Suburban across town without incident. When I got home, I took it to the car wash near my house. I washed it pretty thoroughly. Maybe a little too thoroughly. After I finished, it wouldn't start. Now it runs rough again, just like before.
The thing is, if it's water, how is the water getting into the tank? Is this going to start happening again in the fall?
Chuck
Seattle
At first I didn't know what the problem was, so I took it to a shop where they seem to have a lot of customers with trucks with Chevy 350's. They ran some diagnostics on it and told me they couldn't find anything wrong, but from my description they suspected water in the fuel. I figured rainwater or condensation was somehow getting into the tank. The tank might have pinholes, or the rubber seal around the sending unit was bad, for example. Someone had cut a hole in the deck above the sending unit, and when I filled up the tank, if the carpet wasn't in, you could smell gasoline inside the cabin. Also, crap would fall onto the sending unit, which I figured couldn't be good for it.
To get it running again, I'd put a bottle of Heet (isopropyl alcohol) in the tank to solubilize the water in the gasoline, and a couple of hours later it'd be fine. Then it would rain again, and I'd put in another bottle of Heet. It got so I'd run out and put in a bottle of Heet while it was raining.
This got old, and I was buying a lot of Heet, so when the weather turned warm this summer I put in a new tank and new fuel lines. I replaced the filler hose, return hose, and sending unit with all new parts. However, the tank I removed didn't seem very old, like it had been replaced, and I couldn't find any holes in it. The sending unit seal looked good. The hose clamps seemed tight.
While the tank was out, I also welded up the hole in the deck above the sending unit.
I finished yesterday, and drove the Suburban across town without incident. When I got home, I took it to the car wash near my house. I washed it pretty thoroughly. Maybe a little too thoroughly. After I finished, it wouldn't start. Now it runs rough again, just like before.
The thing is, if it's water, how is the water getting into the tank? Is this going to start happening again in the fall?
Chuck
Seattle
