First Post, First adventure working on one, some fuel related issues I need help on.

Hello all. First time poster. A friend of mine has a shop and works on cars moonlighting. One of his customers picked up a Delorean at an auction that wanted it gone through as it has been sitting for some time. We pulled all the old fuel out, changed filters, plugs, etc. Long and short this car has been butchered. We do have a manual. I won't go into all the crap that we found like a fuel pump that is obviously not original installed.

What we are experiencing is the car is running very rich at idle, rough idle with an occasional throaty backfire that appears to be coming from the RH side of the engine exhaust (looking from back of engine). We verified each cylinder is firing and set the timing. Attempted to set fuel mixture using dwell meter. It will not move off of a solid 40 although we had the 02 sensor disconnected as I misread the manual I believe. I think this should only be disconnected if one has the tools to set the CO2. Also noted that the part (sorry I don't remember the correct terminology) that has the two vacuum hose going to it that controls vacuum advance has been bypassed mainly I believe because one of the wire terminals is broke off. As the car warms up it seems to get a little better but it is still rough.

One question I have is related to the three brass fittings on the top front of the engine. As I read the two most forward are bank air adjustments. Manual is somewhat misguided in that in one section it states that any adjustment wont have an effect due to electronic control and then another section states not to mess with them. Unfortunately we did. I set down last night and studied the manual in peace to get a better understanding of things. I wanted to confirm the most aft fitting will adjust engine rpm.

I guess what I am looking for is where to start and what to check. Never really messed with a beast like this. It is very obvious it is running rich as it will burn your eye balls out. The first time I played with the mixture screw just forward of the injector manifold, to get it to smooth out I had to crank it in considerably which caused the converter to glow red hot so we backed it out until it killed the engine and then turned it just enough to keep it running. Have been checking posts out on here to help our cause.

Any input is appreciated.

You can not adjust idle RPM if your idle system is working. That RPM is preset to 775 RPM.

The three brass screws should be closed. (lightly seat them clockwise).

Mixture adjustment needs to be adjusted with a dwell meter if the lambda system is working. If you just set it for best idle, you will be running very rich.

Because the car was "sitting" for a long time it will have a lot of fuel system problems. Among them will be injectors that don't spray properly and a stuck fuel plunger. If it runs at all it will run very rich and cr-ppy. To fix the stuck plunger you take the mixture unit off and forceably remove the plunger very carefully without damaging or scratching it and then clean with Acetone so it can slide smoothly in and out of the mixture unit. For the injectors you need to have them cleaned in an injector cleaner/tester. Often they can be cleaned up but not always, you may have to replace some or all of them. The O2 sensor will probably have to be replaced if it is even hooked up. Many times it is disconnected. If the car has anywhere near 30,000 miles on it or more you probably need to check the valve clearances. To attempt to adjust the duty cycle for the Lambda system you will need a full-blown tune-up so the motor is OK to tune. You cannot "adjust" the motor to run well. It has to run well BEFORE you adjust the mixture. If the tamper plug is still there the mixture is probably very close to where it needs to be so don't touch it. If the plug is removed you could be WAY off, that adjustment is VERY sensitive, a tiny amount makes a large difference. The part with the broken terminal is the vacuum advance solenoid and should be replaced. Refer to the vacuum diagram on the engine cover.

Not sure which manual you have, but the workshop manual can be downloaded here: http://dmctalk.org/showthread.php?28...Engine-Manuals

In it, you'll find a good write-up as well as several illustrations of those brass screws you mentioned on around page D:01:03. This is in the fuel and emissions section and it explains what those screws are meant to do and also what they no longer do as part of the PRV set-up in the DeLorean. All three snug closed is best.

As Dave mentioned, you need to get the idle system components working as intended and this will mean returning any hacked up wiring or features back to design. We can speculate what to do to correct a problem with a certain component bypassed or disconnected, but the real solution is to get it set-up the way it was meant to be. That'll include the vacuum advance solenoid's electrical and vacuum lines.

Take some photos of the top of your engine as well as the fuse and relay area behind the passenger seat and the group here can help get you started sorting things out on your car.

Thanks for the input. My next thought was to get the injectors out and see what we have. I work at a commercial aircraft repair shop and have some possible solutions to clear up the injectors if there is a problem as we clean and flow test nozzles out of turbine engines. A quick question in the meantime. I had taken a couple of pictures going to connectors which are going no where. Are these test ports? Attachment 54833Attachment 54834

One more question, The mixture screw has been tampered with. Is there a good starting point to begin with as I have no idea how far off the thing is?

"First, thou shalt acquire six glass jars..."

Yep, out of the gate going to check valve clearance and injector pattern for a start. i do believe the Lamba system is at least somewhat operational as one can feel the vibrations with key on not running.

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Originally Posted by Peno67

Yep, out of the gate going to check valve clearance and injector pattern for a start. i do believe the Lamba system is at least somewhat operational as one can feel the vibrations with key on not running.

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With stock wiring, the lambda system only gets power when the engine is running. What you hear is probably the idle motor which will hum with just the key on. The frequency valve (FV) is on the passenger side valve cover. The FV is what will buzz when the lambda system is running.

Quote:

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Originally Posted by Peno67

Thanks for the input. My next thought was to get the injectors out and see what we have. I work at a commercial aircraft repair shop and have some possible solutions to clear up the injectors if there is a problem as we clean and flow test nozzles out of turbine engines. A quick question in the meantime. I had taken a couple of pictures going to connectors which are going no where. Are these test ports? Attachment 54833Attachment 54834

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Someone just recently asked the same thing about those unused connectors. The comment was that they are only used on automatic transmission cars. I'm not 100% convinced about that, but haven't been out to my own car to look for myself. I'd like to tell you one way or the other, but don't know for certain so will wait until someone else chimes in.

I would suggest confirming your ballast resistor is wired up as it should be. Something doesn't look quite right with the connections on the right side, but can't see well enough in the photo to confirm. The right side of the resistor is meant to have a double tab thingy on the top right portion that allows you to connect two of those wires to the one place. Then one on the lower right and one on the upper left. And nothing connected on the lower left. See drawing in this thread:

http://dmctalk.org/showthread.php?40...ll=1#post66530

(Which is a great thread to start reading through and doing some comparisons. The entire colour wiring diagram for the car is in there as well as the bulkhead connections, fuse and relay area and many simplified diagrams breaking down smaller circuits in an easy to see schematic. Well worth looking through if you haven't already).