1990 740 gle gas delivery problem?

joedrt77 · Post by **joedrt77** » 02 Nov 2016, 10:35

He bypassed the under car fuel pump, and just put a 43 psi pump in the tank, so it's just got the one pump in the tank, wonder if that's the problem?

lummert · Post by **lummert** » 02 Nov 2016, 14:30

Maybe not enough volume or pressure.

joedrt77 · Post by **joedrt77** » 02 Nov 2016, 16:27

No schrader valve to check fuel pressure on this one.

lummert · Post by **lummert** » 02 Nov 2016, 16:36

I permanently installed an A/C Schrader valve in the fuel rail inlet tube on my 1988 760 Turbo using a brass tee and compression fittings.

joedrt77 · Post by **joedrt77** » 02 Nov 2016, 18:38

Great idea, think I'll try it, it probably isn't enough pressure, about the only thing left I haven't checked, was getting the 02 code, gotta get one of those I guess, I try hard not to but still end up throwing parts at it.

lummert · Post by **lummert** » 02 Nov 2016, 21:55

To install a schrader valve in the inlet tube one must cut off the fitting on the end of the tube, drill and tap the hole in the fitting for 1/8" NPT. The compression fitting is 5/16" on one end and 1/8" NPT on the other. The schrader valve is for R-12 A/C. One compression nut is placed on the tube followed by the ferrule. The fitting is installed into one end of the tee. a 1/8" NPT short nipple goes in other end of tee. the modified fitting that was removed is installed on end of short nipple. Fuel hose connects to the rail fitting as before. Schrader valve installs in side of tee. Use teflon on all pipe threads.

joedrt77 · Post by **joedrt77** » 03 Nov 2016, 06:35

Wow, didn't realize there were so many steps, I'm pretty sure I would mess up somewhere. Think I'll try the fused jumper on the fuel pump relay, to see if it stays running for longer than a few minutes, wonder what gauge wire should I use, did you use a regular 30 a car fuse or a different kind of 30 a fuse on yours?, thanks.

joedrt77 · Post by **joedrt77** » 05 Nov 2016, 08:57

Anyone have good results, with a universal one wire o2 sensor on these? thanks.

lummert · Post by **lummert** » 05 Nov 2016, 15:29

joedrt77 wrote:Anyone have good results, with a universal one wire o2 sensor on these? thanks.

This would result in a longer time before going to closed loop.

joedrt77 · Post by **joedrt77** » 06 Nov 2016, 15:31

It's back to starting for about 1 second on starting fluid, new cps, new power stage, tested or bypassed both relays, 12 v. at coil, 11.95 v. at f i connector, going for new spark wires next, going to try to test fuel pressure, if it's possible without a schrader valve.

1990 740 gle gas delivery problem?

Re: 1990 740 gle gas delivery problem?