Chances of fixing ECU issue by checking Ohm's etc ?, stock 1.7 D-jet ECU Options

[Literati914]

The problem - I have a stock 2.0L d-jet ECU that starts and runs my 1.7L engine just fine, though I suspect that the engine's running too rich with it .... and I've read of the wrong ECU causing hydro-lock to these engines. So, I'm kind of afraid to even start the engine on this ECU.

I purchased a used 1.7 ECU a few weeks back - $40 off the Samba but there were no guarantees as the guy said he purchased an old VW repair shop that it came out of and had no idea if it worked.

So, I vaguely remember a video posted (somewhere?) where the guy was diagnosing a no start issue by running through all the pins of the ECU and checking Ohm's, continuity etc. I can't find the video now unfortunately. I know there's a special D-jet testing machine - but would finding an off electrical value not allow for repair inside the ECU? I haven't opened this 1.7L unit up yet - it may have obvious damage. I was wondering if it's even worth breaking open?

[Superhawk996]

The wrong ECU will not hydrolock an engine unless it’s defective.

Continuity checks are useful for troubleshooting wiring to the ECU but unless you’re intimately familiar with component level electronics repair, schematics, and have the equipment to troubleshoot (signal generators, oscilloscope, etc.) the chance of simply “findling” something wrong internal to the ECU is practically zero.

[Superhawk996]

You need to figure out what 1.7L system you have

The 73’ 2.0l system did use the 1.7L ECU but with a unique MPS, CHT, and CHT resistor for the 2.0L

The other year 1.7l use different ECUs

Spend the time to understand that components your using and use the Anders part chart and compatibility matrix

Generally speaking parts are not mix and match

[Literati914]

You need to figure out what 1.7L system you have

The 73’ 2.0l system did use the 1.7L ECU but with a unique MPS, CHT, and CHT resistor for the 2.0L

The other year 1.7l use different ECUs

Spend the time to understand that components your using and use the Anders part chart and compatibility matrix

Generally speaking parts are not mix and match

Yea, I did all that before purchasing the ECU from samba.. didn't just randomly buy an ECU. I got the 021 A / 013 unit for my '72/1.7 . I looked at components but will double check them. I got the hydro-lock comment from @Dave_Darling in a post he'd made several years back. .."I had a period where I was swapping ECUs to see if they had any effect on how the car ran. One of them did--it hydro-locked the motor with fuel! .."

ps - I can hear the fuel pump run for a second or so, with the 1.7 ECU as I should.

[JeffBowlsby]

Send it to ECU Doctors in FL. They will test it and can repair it if necessary.

[Literati914]

..
The 73’ 2.0l system did use the 1.7L ECU but with a unique MPS, CHT, and CHT resistor for the 2.0L

Hey @Superhawk996 , I've been reconsidering what you wrote here .. and I think you're on to something. My good ECU is the '021 E / 037' unit. The info @ PBander's site is a little confusing (to me any way) on the subject of shared ECU's amongst the '72-'73 1.7 and 2.0L. There is a NOTE over in the right hand column that reads "Note: Use only the CU13X or the 022 906 021 E (Bosch 0 280 000 037) ECU with the 1973 2.0L engine."

I read that to mean that it's not for the 1.7 at all - but that's not the case as it is listed w/ 1.7 in the left column. So, my mistake, thanks for getting me to look at that closer!! This ECU will work.

[Dave_Darling]

. .."I had a period where I was swapping ECUs to see if they had any effect on how the car ran. One of them did--it hydro-locked the motor with fuel! .."

One of the possible failure modes for the output stage in the ECU is that it "forgets" to turn the injectors off. So it tells them to open, and then just leaves them open. Ugly problem when it happens intermittently when trying to start. Would probably be a much worse problem if it happened at speed on the highway, though.

--DD