Still Can't Get this Thing to Start #2

[ZVOLV]

Originally Posted by OldCarNewTricks

The suggestion for use of a test lamp was very helpful, thank you. It simplified the process.

I'm glad that you got one and have been using it. "Batteries not required".


Post back when you get the thing running.

[OldCarNewTricks]

Originally Posted by bobxyz

Oh, I was thinking it was a little resistor, instead of a bigger wire wound resistor. I'd guess that the colors are yellow, violet (instead of grey), silver, gold, which would be 0.47ohms. This is still a pretty tiny resistance to be used in old designs. 4.7ohms (yellow violet gold gold) would be more common. I'd still get another ECU, and make the original a spare if you want to repair it later.

I took another look at it. I was wrong. The "grey" is actually the second ring that is discolored from heat. This resistor must have split open from heat. It's burnt. On the other side, what's left of ring #2 seems to be sandy brown colored. It seems to be about the size of a 3 watt.

[OldCarNewTricks]

Woohoo! It runs. Turns out the ECU was the issue. Thank you to 2manyturbos for getting that replacement to me so quickly. Sounds to run a fair bit better than before, as well.

[2manyturbos]

Cool. Your test results pointed to the ECU. I'm glad you have it running now.

[84B23F]

Originally Posted by OldCarNewTricks

Sounds to run a fair bit better than before, as well.

Might have the ECU for B23F higher compression engine:-)

[OldCarNewTricks]

Drove it home finally. Bit sketchy with all the guage cluster lights out and the blower motor that died on me. But its home now, so time to get to work on all those smaller issues.

[ZVOLV]

Good diag. Glad to help. Thanks for posting back.

[John242Ti]

Originally Posted by 84B23F

Might have the ECU for B23F higher compression engine:-)

LH ECU is the same for high and low compression. 1983 is a 503 number, 1984 is a 510 number, I'm assuming because of the added circuit on 1984 cars for the heated O2 sensor. OP's car is an Aw70 car, if I remember correctly, so it's already a flat top piston B23F engine in there, unless swapped.



Ignition box is different on low compression engines. More aggressive advance curve.

[84B23F]

Originally Posted by John242Ti

LH ECU

ECU table suggests 503 is for NA 1983/1984, but I've wondered if engine program was twitched between AW70 and stick versions...since engines mated to AW70 were higher compression on 1984 (on engine I own).

Increasing the compression ratio changes the mixture density, but knock sensor may compensate so lower/higher compression engines work ok with 503 LH ECU.

I do know a rebuilt 1984 B23F that was mated originally to AW70 works just fine when installed in a 1993-940 with Rex-Regina, using Bosch 0 280 155 746 injectors ; of course, a CPS was installed on B23F.

[2manyturbos]

Originally Posted by 84B23F

ECU table suggests 503 is for NA 1983/1984, but I've wondered if engine program was twitched between AW70 and stick versions...since engines mated to AW70 were higher compression on 1984 (on engine I own).

Increasing the compression ratio changes the mixture density, but knock sensor may compensate so lower/higher compression engines work ok with 503 LH ECU.

I do know a rebuilt 1984 B23F that was mated originally to AW70 works just fine when installed in a 1993-940 with Rex-Regina, using Bosch 0 280 155 746 injectors ; of course, a CPS was installed on B23F.

Suggests is a good term. That ECU table is a crap shoot. Here is just one example of what I mean.

LH 2.4 -016 0 280 000-556 B230FD 1989 (EGR) 1989-1990 (EGR) - California / EGR Model: -937, -967 and -954 are suitable.

The B230FD didn't appear until 1993. A 556 is an NA 240-740 ECU with EGR. The suggested replacement ECUs are all 740-940 Turbo ECUs. The 937 and 967 are both non-EGR turbo ECUs. Suitable replacements would be a 933 or 946 NA ECU with EGR function. John is correct. 1983 US market NA 240s got the 503 ECU and 1984 got the 510.