1977 280Z Fuel Pump Problems? Kind of a longish story.

[azuka]

Just spent some time looking at things. Would you believe that someone put in a new fuel pump, but it is not attached to anything? Just resting on some bar? I can grab it with my hand and move it around and reposition the damn thing.

I'm thinking the Fuel injection relay may be bad, but it is just this thing under the dash to the left of the driver's knee. How can I test the thing before laying out $80 or so to get a new one that I might not need. Some issue goes for the Ignition Control Module. I'm not sure how to test one of these before spitting out a couple hundred.

[Zed Head]

I've never actually tested the ignition module but there is a procedure. Here's a piece.

www.xenons30.com/reference

[djwarner]

I bought replacement floor pans and rails and hired a local welder with experience in this kind of thing to install.

OK. When I picked up the car he told me that the fuel line had sprung a leak and he had repaired it, but then it sprang another leak and he decided that he probably should not be the one to fix it.

Just a newbie reading this for the first time. From your story everything was fine until the welder worked on it. How did he repair what in the fuel line? Sounds like you have at least two problems - no fuel flow and no spark. I assume that you have followed the suggestions above and verifed the electric pump is actually running. Both the pump and ignition are electrically driven - could there be a common problem? Either power - or chassis ground? The welder was doing some major welding and could have introduced a ground problem.

[azuka]

Yes, I agree. Everything was 'fine' mechanically before the welder got involved. But of course I know that old parts can go bad at any time.

I went back to basics this afternoon, seeking confirmation that the pump was pumping out gasoline. Turned out that it was NOT! I detached the hose from the fuel filter and inserted a clear tube from there into a gas can. When I turned the engine over I got no gas.

Right now the carpeting is out of the car and the passenger seat is out too, making things easier to see in some respects. I saw some spliced wires that I was able to confirm went to the fuel pump. The welder must have cut the wires to put in the new floor pans, and then added a length of wire to splice onto it. One end of the wires had the tube connections that you crush... no problem. THe other end of the splice he must have run out of those connectors, so he twisted the wires together and used something like scotch tape to insulate the connections. Kind of shabby in my opinion, but on the good side, once I removed the scotch tape the joins made for easy access for testing. Was unable to find any current to these wires while turning the engine over. But when I connected the 12V battery to the wires (black - negative, green - positive) the pump immediately got busy and started pushing gas into the gas can.

So.... the pump is good, but needs to be properly stabilized rather than left banging around. I need to find out why I'm getting no power to the fuel pump. I figure that my spark testing method may have been faulty, so maybe I am getting spark, maybe not, not sure.

At this point I'm thinking that the fuel relays may be faulty. Maybe the injector control module. Maybe both.

Not sure how to test either one.

[djwarner]

Good start, May I suggest you verify the chasis has a good connection to the negative terminal of the battery.

[azuka]

I ended up buying a new fuel relay and new ignition module. I already had a replacement ECU from a parts car, part number matched on both ECU's. I figured I may as well buy them, and if they didn't make a difference, I could always resell them and get my money back, or at least most of it.

I replaced the fuel relay, and tried starting, then I replaced the ignition module.... no change still, then replaced the ECU.... still, no change.

So I'm back to square one. I'm going to rethink this. I need to check again to see if starting fluid sprayed into the manifold will do anything. I need to double-check the spark to prove whether or not I really AM getting spark. Questions.... could the ballast resistor for the coil be bad? Could the distributor need replacement?

[azuka]

Here's an update. I got a mobile mechanic out today to help me. After looking at things he told me that it looked like the leaky fuel line was keeping the engine from getting fuel, and once that was replaced, we'd be able to get the car started and all would be well. He was pretty pumped up about being able to work on a Z car!

Well, we replaced the fuel line. Something weird is going on with the power to the fuel pump. We were able to determine that 12V were present in the wires going to the pump. but the pump won't turn on. Finally, we connected the power directly to the fuse box so that when the key is in ON or START position, the fuel pump is running. Not quite the way things should be, but better than nothing I guess.

So now, I am able to start the car, and it runs for a few seconds and dies. After fussing around a bit, it hit him that perhaps the problem is air in the gas line and that we need to wait a few hours for gravity to take care of that issue. So I'll wait a couple hours and try again.

Does this make sense?

[Hardway]

Glad to hear you are making some progress. As far as having air in the fuel line, you should not have to wait a few hours for that to be resolved. Since the system is pressurized you could loosen the fuel line where it connects to the hoses that go to the injectors. With a wrag or something around it run the pump for a few seconds, be careful since it will probably spray in all directions. Once you clean up the gas re-tighten the line and try again. It should not take much to clear any air from the line.

Another less messy option it to just run the car, let it die, start it back up, let it die until the air is out. It should not take more than 2 cycles of this to clear the air.

On a side note, I have worked on a lot of different EFI cars and air in the lines has never been an issue. Even after having a system open to replace lines, injectors, etc. Once everything is hooked up I would let the pump prime the system, verify there are no leaks, and turn the key to start. Barring any other complications the car usually started right up and settled in to a nice purr at idle.

[Zed Head]

Firstly, I would not use that mechanic again. Unless you didn't understand what he was saying, he does not seem to have even the basic skills required to work on EFI systems at all. Power in the wires but can't make the pump run, leaky fuel lines stopping fuel from reaching its destination in a 36 psi EFI system with a return line, air in the lines stopping flow, waiting for gravity - all bad.

Edited my previous comments and gave the guy the benefit of the doubt. He might be a great mechanic for carb'ed cars.

Based on the last statements, that it will run for a few seconds then die, even though the pump is running, it sounds like your injectors might not be firing and the engine is running off of the gas from the cold start valve. Or the fuel pump inlet could be clogged, but it would probably run for a more than a few seconds if so (note that "few" generally means about three). Just guesses. Looking back in the thread, it seems like it hasn't run since the welding was done. Maybe something got fried in the ECU.

Keep looking for someone that knows how to work on old EFI systems, not someone excited to work on something they don't understand. Download the FSM, print out the pages of the Engine Fuel chapter and let the real mechanic do some component testing. All of the proper tests are described in the Engine Fuel chapter.

Edited December 7, 2012 by Zed Head

[EuroDat]

I second Zed' post 21. If that his diagnosis than stear clear of him. He will only cost you money and probably make it worse.

[azuka]

In a couple minutes I'm going back out to the car. First, I'm going to double check to see that all fuses are good. Then I'm going to fire it up. If that's no good (as I expect) I will swap out the ECU and see if that makes a difference.

At least the leaky fuel line has been properly fixed. I found out why the welder had such a problem 'repairing' it. He used brake line tubing to do the repair. Or at least that's what my mobile mechanic says.

Edited December 8, 2012 by azuka
additional info

[azuka]

Oh yeah.... while I'm at it. I'm going to check to see if any of my fusible links are bad. At least I can clean up the contact points to make sure I have good connectivity.