Engine swap starting issues

Hello everyone,

Having a little problem getting my engine from a '96 Passat to run. Initially there was no fuel coming from the injector pump due to the 109 valve not receiving power. Did some digging around and found two no start conditions for the engine where it wont run. The first being no signal from the air-mass flow sensor, and the other from the modulating piston movement sensor. I checked and found no voltage to the piston sensor and found the issue was a faulty connection at the ECU. I got that sorted out and now the 109 valve receives 12 volts for a split second when I turn the key on. I checked at the ECU and it only provides split second power from the ECU, so I don't think it's a faulty connection. I don't think it's the 109 relay because I put in all new relays and fuses. I need to check the MAF, but does anyone know any other kill conditions for the engine? I don't think it would be the immobiliser (considering I paid Malone tuning to remove it) and I'm almost at my wit's end. I could bridge power but I'd rather treat the cause than the symptom. Any suggestions?

I have an ALH swap I did myself. I don't know how similar these are but I bet they're close enough. I triple checked my wiring and have only had one problem after almost two years, a broken signal wire to the IP in the first week. I haven't dug into how it all works, I just followed the Bentley schematics and hooked it up right. That being said, it sounds like 109 should get constant power no? Doesn't it get switched on by the key, and the 109 powers the ECU? Why does yours get power from the ECU?

The 109 has constant power when I turn the ignition on. I just borrowed a scanner from a friend, it's throwing 7 codes.

P1354
P1562
P1163
P1252

The other codes are currently irrelevant to the engine running. Most of these have to deal with the IP, so it's either my wiring harness not receiving proper QC when I had it custom done, a couple of loose or damaged wires (they all looked good on a quick once over), or the most dreaded possibility of the injector pump being toast. I know that if there's an issue with the modulating piston displacement sensor, the ECU will generally prevent the engine from running. Considering there are three codes coming from the IP, I'm going to assume it's a wiring problem because those systems are all on different circuits, I find it more believable that there's an issue with the wiring harness, considering I already found a faulty connection at the ECU. I'll tinker around a bit and post an update once I've made some progress.

You may have done this already, but it never hurts to clear the codes and then see which ones come back again.

When doing a swap / troubleshooting it's possible for codes to be thrown that get fixed a bit later, but they won't clear themselves automatically.

Gotta clear codes manually to make 'em go away... the ones that come back still need attention.

Found part of the problem. The connector at pin 52 (might not be the right number, this is off the top of my head) has a bad contact. No continuity between there and the pump, but probing the wire directly behind the ECU connector has continuity. This made me check a few more connectors relevant to other DTCs, and it's the same situation. With the exception of the fuel temp sensor, the resistance is out of range for what's considered serviceable. So far, looks like all but one of my issues are wiring related.

Out of interest are you using the original 68 pin ecu with the AHU engine ?
The ECU would show up "Engine Start Blocked By Immobilizer" if there was an immo issue

I'm using a 68 pin with the AHU, however I'm not receiving an immobilizer code, and I got the ECU from Malone tuning with the immobilizer (supposedly) removed. I'm going to borrow a buddy's ECU tomorrow and see if that works. It's now sending power to the fuel shut off valve, however immediately cuts power when I begin to crank. So far, no CEL or DTCs when I use the scanner. I'm getting a new crank position sensor, because the live data test wasn't showing any RPMs when cranking. The engine uses the needle lift sensor as a substitute speed sensor, but if both fail it will shut down the engine. Fingers crossed i get some progress soon.

Whiskey_Mike said:

The engine uses the needle lift sensor as a substitute speed sensor, but if both fail it will shut down the engine.

Click to expand...

Unfortunately, that’s been proven to be incorrect data. When my speed sensor died, the engine stopped. Others tested, by unplugging the injector and their engine stopped.

Did you test the impedance of the sensor? From memory, it should be between 1k and 1.5k ohms.

-Todd

Glad to see you're getting the problem identified.

FYI I'm not sure what you're using for wiring identification but my notes on the matter indicate that the Mk3 Bentley has some errors in the diagram regarding the G149 sensor. I've mapped out the AHU and 1Z harnesses completely and there are some inconsistencies between what they've published and what reality is for the 68 pin ECU with these two engines in the US cars.

Hope you get it figured out.

Steve