I went ahead and attempted to re-do all of the continuity checks that I wasn't able to get the proper readings previously. Particularly the IAC , fuel

injectors and the throttle switch as sdewolfe had suggested in my previous thread. First, the muti-meter that I have is an old Fluke 73 that doesn't have

a REL or zer-out button on it. So I tried to cross the leads and laid them down so as not to disturb the reading. I even had to close the doors as well as

the hood on the car because the wind was blowing and the resistance readings were all over the place. I made sure that nothing was touching anything it

wasn't supposed and I'm still not too sure about these because it was so sporadic when the meter would calm down and settle on a number for a few

seconds and as soon as I was getting ready to write it down, it would change. I was, however able to get a good reading on the throttle switch. So the next

thing I tried out of frustration was to try one of my spare ECU's from a donor car and still no-start. I was sure to disconnect the neg. batt cable before

connecting the spare unit. Anyway, I have a few questions that I was wondering about. Since my first donor (and my daily driver)cars are '83s they both have

ECUs that part#s ends with the #s 503 and both of my '84 cars ECU's part#s end with the #510. When I couldn't get this car to run originally I swapped out the

503 for the 510 and then the car ran rough. My first question is obviously, what's the difference between the 2? I also noticed that on both of my '83's I

have yellow top fuel injectors and on my '84's I have black top injectors. On the problem car I have the yellow top injectors. At this point I am grabbing at

straws! On a side note, I went out and spent $45 on fittings to get my fuel pressure gauge to be able to tee into my fuel rail to do a pressure check. But

after looking at the Bentley again I realized that I have to have the car running to do this test so that'll have to wait. Anyway, does anyone here have

any further advice/ideas? Thanks, Charles BTW, the donor car ECU tha I swapped in was a 510.

Howdy,

"and the resistance readings were all over the place."

Usually an indication of a bad lead or bad connection with the circuit under test. You really don't need a button to zero the display. Just note what the reading is when you hold the two leads together and be sure to subract that value out to get your true voltage/current/resistance.

" I was, however able to get a good reading on the throttle switch."

How about the IAC? Did the wiring to the injectors check out OK?

I cannot answer your question about the various ECU numbers. There are a lot of folks here who can though. Try posting a thread with a title like "510 and 503 ECU" and find out if the two you have are compatible with your other hardware.

--sd

How doin' Mr. Shannon sir...

I've used both interchangeably in my 83 and 84 LH cars. My understanding was the 510's program took into account the probable use of the heated oxygen sensor introduced in 84.9, but that never explained to me why I seemed to find 510 ECUs in cars without the heater harness. Some will tell you the 510 is an improved 503.
--
Art Benstein near Baltimore

Always keep your words soft and sweet, just in case you have to eat them.