I'm back! Now, for some fuel injection questions...

ubercrap · Post by **ubercrap** » Sat Mar 24, 2007 11:30 am

OK, I have had a lot of things happen in the last 4 months or so, I was laid off from my job, I sold my house, and got engaged, then moved. I just went on a very promising job interview yesterday, should know within a week. The car stuff has largely been on the back burner. I tried to keep up some posts on the samba as I am the moderator there. To those people I was making the poly radius arm bushings, I am so very sorry for the massive, ridiculous delay, they should be out to you shortly. Though I will be picking up my wagon from storage in Missouri at some point soon hopefully, I now have my best 412 sedan in Atlanta that I am trying to get running again.

OK, enough of the personal stuff, let's get down to some car stuff. To refresh you memory, this '74 412 2dr. sedan has original D-Jet injection. It has all new fuel and vacuum hoses, cap and rotor, pertronix installed, new plugs and plug wires, and new injectors and seals. For now, I have a used fuel pump in there that was sold to me as good, as several of the ones I had with me were no good. As far as I know, the car has been sitting for 7 years or so.

What it is doing: I've got a fuel pressure gauge on the rail. The pump turns on when you turn the key and pressure builds when the car cranks, but it won't start. If I run back and look, the pressure drops rapidly (within a minute) on the gauge down to about 5-10, and then slowly to 0. From Ray's suggestion in back posts, I pinched off the return line partially (at the front by the pump) and built up pressure again. It dropped just about as rapdily as before. Then, I completely pinched the return line closed and turned the key until I had about 32 psi in the system and then let it sit. It dropped more slowly this time to about 20 psi, and then a little more quickly down very low. This took about 5 minutes.

Are both the fuel pressure regulator and the relief valve on the pump bad? I didn't see any external leaks anywhere.

raygreenwood · Post by **raygreenwood** » Sat Mar 24, 2007 2:19 pm

You are about spot on. It is usually rust flecks on both the regulator and teh pump relief valve. I have more thoughts on this...but net time is very expensive where I am right now (Egypt). More later in the week. Ray

ubercrap · Post by **ubercrap** » Sat Mar 24, 2007 2:29 pm

OK, I'm assuming the pressure regulator being shot will keep the car from running. That is about $50, so not too big of a deal. Now, what about the pump? Will that need replaced too? Or can I just crank the key over a few times until pressure builds every time I start it (until I have the money for a new pump)?

wildthings · Post by **wildthings** » Sat Mar 24, 2007 8:08 pm

If you are getting normal pressure at any point while cranking it should start. Pressure bleed off should just delay starting until the pressure is built up. If you have crap in either your pump check valve or your pressure regulator, then it is likely that you have crap clogging one or more injectors as well.

Have you checked the impulse signal to the injectors? No impulse, no fuel delivery! If you have impulse then check the spray pattern to verify that the injectors are actually passing fuel.

ubercrap · Post by **ubercrap** » Sun Mar 25, 2007 10:04 am

Hopefully the injectors aren't clogged, they're brand new. I haven't checked the impulse signal or confirmed if the injectors are spraying yet, I'll check that soon (as soon as I figure out how, electrical stuff is not my forte).

raygreenwood · Post by **raygreenwood** » Mon Mar 26, 2007 1:23 pm

Yep, just bump it about thre times then start. You can....remove the aluminum cap form the pump relief valve and install a sealing screw instead...just deleting the valve. All it i for is both a check valve and a safety valve in case a line gets crimped. Ray

ubercrap · Post by **ubercrap** » Wed Mar 28, 2007 7:41 pm

OK, I pulled an injector and turned the car over and at least the injector I was testing was firing as it should, and I'm assuming the others are too as they are brand new. Last I tested awhile back, I was getting spark, but I will confirm that nothing has changed.

I rechecked my static timing, and I think it is on. This is something that confuses me. I had the distributor out in the past so assume that anything could have gotten messed up. I basically took the distributor out again and started over. I rotated the engine until I saw the 0/TDC mark. Now, according to the manual I have, I need to be seeing not only the TDC mark, but in the position that the valves on cylinder 3 have one just closing and the other just opening. I got them to the point that they looked both to be in the same position. This is the best I could do by myself. I can't turn the engine at the same time as looking at the valves. As far as I can tell, I ended up with everything in the exact same position that I had them in. What else can I do to confirm that I have cylinder 1 TDC on its compression stroke?

The next thing I want to check is the CHT resistance. First of all, the wiring was totally messed up and broken going to it. I crimped new connectors on the wire that went from the plug to the CHT and to the wire that connected to the plug. I measured the resistance of the modified wire and it showed 0.5 ohms. I assume that with that low of resistance that the crimping new connectors was OK? It seems like it would be fine since the CHT operates in a range of 2300 to 70 ohms, correct?

Anyway, what size of socket do I need to get the CHT out? I don't have that big of a deep socket.

wildthings · Post by **wildthings** » Wed Mar 28, 2007 9:12 pm

If you turn the engine 30° to either side of TDC for #1 cylinder then one of the valves on #3 should be open and the other should be closed with free play. Both valves for #1 should still have free play at 30° either side of TDC.

ubercrap · Post by **ubercrap** » Thu Mar 29, 2007 8:58 am

Thanks, I check everything and report back.