[DML] Yellow "D" and mysterious fuel problem

["RYERSON,TERRI" <tryerson@xxxx>]

There have been a couple of posts recently regarding a yellow DeLorean seen in various places. One of these places was mentioned by Paul Feine, and was the Consolidated International warehouse in Columbus Ohio. I suspect that the yellow "D" mentioned is the one that is now laid up with a strange problem in my garage in Akron Ohio. I purchased this car locally in late July of this year and it is in excellent condition throughout, except for the problem mentioned below.

The extremely puzzling problem is as follows, and suggestions will be greatly appreciated!

The difficulty began when the car died on the freeway a couple weeks ago: not a slow death, it just quit w/o warning. After towing home, and checking all the simple things ( fuses, connections, etc. ), I discovered that there was no fuel pressure even though the pump was running.

After a check of the fuel tank internal lines and filter, it became more apparent that the pump had indeed failed. At this point, having nothing to loose, I cut the top ring off the pump in order to gain access to the internals for inspection. This showed a fairly large amount of what was apparently deteriorated "O" ring material all throughout and particularly inside the vane pump assembly.

After installing a new, exact replacement that my wife secured locally, the car ran normally the rest of the day ( approximately 15 miles ) that the new pump was installed. The next day however, was a different story. A short time after leaving home on the second trial, the engine began cutting out and in violently. When the accelerator was depressed more than approximately 1/4, the engine began cutting out and in and releasing the accelerator to less than 1/4 throttle stopped this effect. As long as less than 1/4 throttle was used it ran fine.

Although I don't have a suitable fuel pressure gauge to make certain, it appears that there may be a problem with the "control" fuel pressure from the control pressure regulator. This theory is because that the air flow sensor plate is now quite difficult to move while the engine is running, and when the throttle is manually "snapped" full open does not move downward nearly as much as it had previously when the engine was running well. This probably confirms that a lean running condition is now in effect.

I've checked the oxygen sensor, frequency valve, thermo time switch, thermal vacuum control valve ( lambda thermal switch ), and lots of wire connections. All of these items appear to be functioning as they are intended with the possible exception of the frequency valve. The frequency valve is indeed cycling at the appropriate rate, but the duty cycle appears to be too long, which could explain at least part of the lean condition.

I plan to verify that the fuel return line is not restricted, but after that I'm completely out of ideas, and at this point have probably missed something simple.

If anyone has suggestions about all this I'd certainly appreciate the help!

George Ryerson

Tryerson@xxxx
DbPgmr@xxxx