The leak is either the upper injector seal or the weld on the rail. It's time to strip it back down to expose the fuel rail.

I'll need to pressurize the system when I get it stripped down, but am wondering if there's an electrical lockout for the pump if any sensor signals are missing to the ECU. IOW, I plan to disconnect the coil and spin the engine to get fuel pressure..... wondering if the TPS/IAC/MAF signals are required by the ECU to pass current to the pump.... anybody know for sure?

Frank

1 hour, 15 minutes for tear-down.... not bad.

The question wrt an electrical lockout for the fuel pump is answered - the ECU doesn't cut the fuel pump with the IAC/TPS/coil unplugged. The source of the leak was very obvious - the welded hole on the fuel rail:



I guess I'll have to drill out the weld and find another way to fill the hole... maybe a threaded plug, but that should be a tough thing to cut threads into. In case I can't clean this fuel rail up, does anyone have a spare '89 fuel rail they want to sell? If so, PM me.

Frank

Take it off..... clean it up.... tig the hole up. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Good idea, Curtis.... I'll try it. I didn't expect that wire weld to leak like that, but it sure did.

Frank

I've been watching the progress of this project for a while. I think it's great that you are doing something different, not following beaten path. It is even better to see that the project is really going to be successfully finished.

About the fuel rails
With some other projects I've had also problems with leaking welded fuel rails. Sometimes fuel rail material is not very well weldable and welding can produce cracks in the material. I don't know is this your situation, but I've found soldering very helpful in these cases.

Also the long, not supported piping at the end of the fuel rails could become a fuel rail fatigue problem in the future.

Good luck, you are almost there!

Thanks.... it's a curse I learned from my father..... question everything....... believe nothing..... and prove things/ideas to yourself.... then you'll know what works. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />



I agree, but could not find a better solution for the fuel line routing - or for the fuel rail. I wanted to build custom (stronger) fuel rails, but the offset fuel delivery bungs necessary to clear the lower intake don't leave much choice except to adapt the OE fuel rail. With a liberal dose of Permatex #2 used as thread sealant, it does "feel" stronger than it looks.



I understand your suggestion - and agree that the material isn't the best for welding - but I have (at least) 3 pin holes that appear to be near the center of the welded hole.... not a bonding issue (I *think*) - more like a gas path during cooling.

Calling all welding gurus:

My welding experience is limited to a few passes of stick welding in college engineering classes about 40 years ago. I've ground the center of the weld in the area of the leaks to a bowl shape.... depth of ~ .050". Is it deep enough for TIG welding to fill - or should I grind until the hole is reopened?


Frank

Frank, I kind of like the solder idea, but I'd braze it for a little more strength, filling the dip you just created, and i'd test it with air pressure in a bucket. Pressure testing with gasoline gives me the willies. Nota Bene sparkems comment.....

I originally asked for the hole to be brazed, but it was welded instead and I thought it looked ok. I took it back today and asked an opinion - he thought either TIG welding, brazing or silver soldering would work. The closest method was only a few feet away, so I asked him to try brazing the bowl I ground. It took about 4 times of filling and grinding before I was satisfied.... it kept developing an edge until he figured out how to brush the rod across to fill the cratering. I hope it's ok now - already repainted:

There's no good way to pressure test off the truck because of the injector holes. Thanks for the warnings, though guys. <img src="/forums/images/graemlins/kewl.gif" alt="" /> I think I'm ok using the fuel pump in this case - without the plenum, everything's in plain view and a fire extinguisher is close at hand. <img src="/forums/images/graemlins/notooth.gif" alt="" /> Besides, I want to see it under pressure up close before I put everything back together. <img src="/forums/images/graemlins/baby.gif" alt="" />

Frank

All back together.... no leaks. It idles fine and revs fine..... BUT... the mechanical fuel gauge on the regulator shows 25psi and the in-cab gauge that runs off of an electrical sender teed into the regulator gauge port (shared with the mechanical gauge) pegs at 100psi. No amount of adjustment on the 1:1 side of the regulator shows a change on either gauge..... weird. I'd have to guess that the regulator is defective and at least one gauge is also defective. I suspect the mechanical gauge is correct. I thought that maybe the electric sender wasn't getting a good ground and rigged an extra ground, but no change. Anyway, I've emailed Corky Bell for his take, so I'll wait a little longer before I drive it.

Frank

Mitsubishi has a fuel pressure test adapter. It sits between the firewall hard hose and the flex hose going to the engine. The test adapter has a schrader valve on it to attach an external fuel guage to it. I have one somewhere in the basement. If you want to use it, let me know and I'll try to dig it up.