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Old 07-13-2018, 10:37 AM   #1478
hgs_notes
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Join Date: Aug 2003
Location: MN
Posts: 5,712
Re: Over 25 Years Later, Finally My 71 C-10 Truck Build

Last summer I had some problems with the motor swap, transmission, etc. but eventually got the truck back on the road. We had a harsher than normal winter (for MN, that's saying something) and really didn't drive it or do anything with it. Spring finally arrived sometime in late May. I drove it once or twice. Then in early June I went for a drive and was thinking that I usually had some plan for a repair or improvement every year and didn't have anything in mind for this year. Mainly because of the struggle last year. I felt it was better just to get some miles on it.

But then on the way home the engine stumbled a bit. And got progressively worse. Then died while going down the highway and I coasted into a parking area for a small cemetery along the road about 2 miles from home. Fuel pump growling and stopping. Welp, I guess I know what I'm doing. After a wait of 10 minutes or so the fuel pump cooled enough to stay running and I drove it home.

That was a new inline pump from FI Tech. There were reviews when I bought it that said the pumps had died prematurely but I put the pump right where my old one was and had no issues with it. Different pump, different results. I decided to upgrade the fuel delivery system with a new tank from a 90 blazer with the in tank pump sump and a new intank pump.

It sat for a month while I gathered parts and got other things done and waited for the weather to improve. The old tank came out without too much difficulty. I wish I could say the new one went in as easily.


The new tank with the newer sending unit. I used a walbro universal in-tank pump (GSS342 with install kit 400-791).


The problems started pretty quick. Turns out the fuel fill inlet on the new tank is a larger diameter, the vent line for the fill is also larger, the new sending unit has special threaded flares for the GM EFI throttle body system that don't really have standard fittings available (at least that I could find while in the middle of the install).

I checked at the parts store for fittings or lines and you can get sections of stock fuel line but it's expensive stuff and doesn't really help with the install because you would just cut it and use one end anyway to connect to the sending unit. So I went to the junkyard and we found a tank where the connected fittings weren't too severely corroded. I could have just cut the fittings off the sending unit and flared the tube (maybe) but the thing costs about $95 and if the level indication isn't working they are not likely to accept a hacked up unit in return. So I used the junkyard fuel line connectors with about 6" of the fuel line. Then I connected to new high pressure fuel line, the same as what I used for the install last year, using brass hose barb couplings.

I decided to keep the return fuel line from the corvette regulator/filter as it was, dumping back into the fuel fill hose so I didn't have to redo that section. It worked so why not. So on that connection on the sending unit I just plugged the attached junkyard hose.

The fuel filler hose was rednecky but should work. The outside diameter of the old hose was about the same as the diameter of the new tank fill tube. Which is about the same inside diameter as a radiator hose. Yes I know it's not rated for use with gas. What I did was use it as a coupler that just wraps around the 2 ends butted together. The radiator hose will see almost no contact with gas. If it fails I'll change it. I had to use what was available to me at the time. If it ever comes to that I'll weld a couple pieces of the correct diameter steel tube/pipe together to make an adapter.

The fuel fill vent line is about 5/8" compared to 1/2" of the old one. I was able to weld a 5/8" diameter fitting onto the steel tube used on the blazer fill vent line and a piece of 5/8" hose I had around.

The wiring wasn't really a problem other than I was short of the correct size butt connectors which meant another trip to the store. I'm 9 miles from town and 20 miles from any major big box stores. The wiring from the sending unit has a single connector for the fuel pump and gas level gage. I cut the connector off because those wires on the truck are on opposite frame rails and I don't have those connectors anyway. I did test that the pump spun before putting the tank in the truck. I had to extend the fuel pump wire a couple feet to reach the wire from the throttle body but that's all that was required. Connected the ground wire and was ready to install the tank.

The only hassle I had getting the new tank mounted was that I didn't realize the new tank was the larger one available. The GM 15A is about 10" deep. The newer style 14B is a 31 gallon tank and about 3" deeper. The straps didn't wrap around the tank and reach the cross brace. I dropped the tank and loosened the front end of the straps as far as I could and tried again. They just barely reached through enough to get the nuts on. But they were long enough, thankfully.


The new tank hangs down more and I'm not thrilled about that. It's about the same look as if you use the 69-72 blazer tank which is deeper but shorter front to back. The square body blazer tank is about 28"x29" so it can be flatter for the same volume. But I do like having the higher volume. I think the 15C tank would have been the same dimensions as my old tank (25 gallon) and had the pump sump because it was for the 87 blazer/suburban. Something to consider if you go this route. Also, this tank probably wouldn't fit well under a short bed truck. I think it can be done but you have to move a crossmember and I think the track bar gets in the way, so if you have a GMC with leaf springs in the rear it might work.

So it's back on the road! I would still like to get the dash pad fixed this summer because the cover peeled up on the passenger side. We'll see.
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