Mk4 Gas Conversion - Have TDI Donor Car

I have a 2000 Jetta TDI that is my daily driver but the body wasn't treated too well before I got it.

I am on the lookout for a Jetta gasser that I can use the body to swap all necessary parts over to so I can escape my car's body woes.

Conversions aren't a big deal to me as I've done several Cummins conversions.

Questions:

• Because of the difference in IMMO2 (2000-2001) & IMMO3 (2002-2003) would this restrict what year cars I could use?
• Being that I have a 2000 model, would there be any issues getting a 99.5-2003 car to swap stuff into?
• What parts are necessary to swap besides: drive train, ECU, engine compartment harness, fuel tanks/lines etc, cluster, pedals & shifter assembly if gasser is an auto, locks/immobilizer if having to work with a IMMO3 car
• Are there any differences to deal with on cab wiring harnesses?

This would be a good set of questions to have answered. I have a couple of possible donors that I haven't proceeded on because they're autos and they're rusty. They're both Y2k model years as well.

There are some guys that can comment - help us out, please!

Cheers,

PH

Hopefully they will see this.
Done quite a bit if searching and never felt like I got these solidly answered.

If you want zero problems or headaches just swap all wiring (body and engine) harnesses over to the new body.

You can have the immo deleted for $50 if you think it would be a problem.

I've done both entire harness changovers and just changing engine harness over. Changing all harnesses over requires gutting the entire interior.
Just changing the engine harness requires adding additional wiring and relays......not hard just time consuming.

Thanks,

That's interesting, I would have expected say a 2000 GLS 2.0/1.8 to have the same body harness as a 2000 GLS TDI.

Have to add in relay 109 and fuse. Also have to add some wiring through the rain tray if I remember correctly

ihredneck said:

Thanks,
That's interesting, I would have expected say a 2000 GLS 2.0/1.8 to have the same body harness as a 2000 GLS TDI.

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Some of it is, some of it is not. The ALH engine has no lift pump, so the wire harness and connector under the back seat is different, and of course the gas cars have a fuel pump relay in the fuse box, and no glow plug relay.

But stuff like the trunk lid harness will be the same. Radio harness is the same. HVAC harness is the same.

Hmmm, that's good to know. I guess pulling the dash wouldn't be horrible, but I wasn't expecting it.
Just means more down time during the conversion.

ihredneck,

I did an ALH swap using a 2002 Golf in to a 2000 Audi TT. IF you trace through the wiring diagrams carefully, you can use the fuel pump relay (on the gas car) in place of relay 109 (on the diesel car). You'll need to trace the trigger wire to the ECU through the 10 pin connector in the cowl (gas car) and make sure it's in the same place as the diesel car engine harness.

You really need a Bentley for the wiring diagrams and a voltmeter to trace wires. I would also invest in a good set of pin removal tools. I bought a set of individual pin tools (each was like a very thin screwdriver) on Amazon. I bet I spent 40 hours looking at wiring diagrams, tracing wiring on the gas side and diesel side, and moving wires in the 10 pin cowl connectors.

Eric

If you just do the engine swap you don't need to replace any body/chassis wiring/harnesses. Swap in the TDI ECU and cluster (immobilizer delete the ECU if the 2000 has immobilizer) and the two TDI engine bay harnesses along with the GP relay. There is a little bit of wiring to do to supply power to the GP relay etc, but fairly minimal. You dont have to pull the dash or do anything in or to the fuse panel mess. About 6-8 pin out connections to switch in the rain tray cowl box and under the dash. I added a small acc type fuse panel to power the 109 and GP relay.
I did my 2003 into a 2003 1.8 chassis this way and everything body/chassis wise electrical works, even the obdll port functions normal. I left the 1.8 intercooler in place as it seemed identical.
The key is to have a complete donor car, which OP said he has. Swap out gasser fuel pump for the diesel fuel pick up unit, rewire the gauge using just the two wires, delete the gas fuel filter, cut out or swap the fill pipe neck, install the diesel fuel filter assembly. A/C compressor hose is different, so swap that as well as power steering pump/rack line. Downpipe and converter will hook up to the exhaust system, although the chassis I used had an aftermarket system installed from cat back.
It's not that difficult. I actually found the easiest wiring work around method on VW Vortex forum, but the guy was also one time a Tdi club member.

Great info guys!
So it sounds like the few wiring details, GP, 109 relay and the immobilizer are the main issues to be concerned with.
Do I have any need to delete the immobilizer if I swap the ecm and keys IMMO chips accordingly?

If the ECU and cluster are moved together, the Immo chips from the donor car should still work, so I wouldn't see an issue.

Assuming that you have VCDS, you could move one chip, and then reprogram the cluster to recognize the rest of chips in the keys that fit that car.

Thankfully 2000 was still Immo2, and the keys don't lock to a specific cluster when they are paired. Apparently Immo3 did, making the chips one time pairing parts.

Very nice to find out these details!

Do you know who was the person of VW Vortex who had the wiring work around?

ihredneck said:

Thanks,

That's interesting, I would have expected say a 2000 GLS 2.0/1.8 to have the same body harness as a 2000 GLS TDI.

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If this were a Mk3 / B4 that would be true. The ABS harness, radio harness, and lighting harness were separate (though they might be lightly taped together in places). However, on the Mk4 cars the whole interior harness is one big thing covered with multiple layers of (rather tough!) tape. You can still split them apart, but it's a lot more work. Plus there are grounds and interconnects in places under the tape.

With both cars you will have all the wires / connectors / harnesses you need. If both cars have the same equipment, your easy path might be to simply remove the entire body / interior harness from the TDI and put it in the 2.0. Yes, the seats and carpet have to come out to do this.... which is a great time to clean them up.

The harness bits that go up for the dome lights might be a bit of a nuisance though.

Another option would be to take apart the TDI harness, remove the wires that aren't in the gasser harness, and lay them alongside the original harness. That would require less interior disassembly.

-J

Front what I have heard, the gasser harness works just fine, just need to transfer over the glow plug circuit and relay 109.

turbocharged798 said:

Front what I have heard, the gasser harness works just fine, just need to transfer over the glow plug circuit and relay 109.

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It's a little more involved than that but not much. I used a 2003 1.8T chassis and swapped in the ECU/cluster, etc from the wrecked 2003 TDI. No chassis harness swap required. A few pin out swaps in the raintray cowling connection box and a small power panel added for the GP/109 relay. As I mentioned prior-everything works. OBD port runs my ScanGauge and VCDS. The radio I'm not 100% sure about because the prior owner of the 1.8 car had butchered the radio wiring harness to install a double din touch screen Pioneer unit. I rewired it to work, but it doesn't shut off with key out or door open-yet anyways.
No need to hack into the chassis harness or fuse panel.

All good info.

jettawreck said:

It's a little more involved than that but not much. I used a 2003 1.8T chassis and swapped in the ECU/cluster, etc from the wrecked 2003 TDI. No chassis harness swap required. A few pin out swaps in the raintray cowling connection box and a small power panel added for the GP/109 relay. As I mentioned prior-everything works. OBD port runs my ScanGauge and VCDS. The radio I'm not 100% sure about because the prior owner of the 1.8 car had butchered the radio wiring harness to install a double din touch screen Pioneer unit. I rewired it to work, but it doesn't shut off with key out or door open-yet anyways.
No need to hack into the chassis harness or fuse panel.

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Can you please shoot me a email or message on here with more info on how you did this? In the middle of swapping everything from my 2002 alh 5 speed wagon into a 2002 2.0 auto. Have everything done other than 109 relay and glow plug harness. Would be greatly appreciated man. Email is chevyfan196@yahoo.com

Alhguy96 said:

Can you please shoot me a email or message on here with more info on how you did this? In the middle of swapping everything from my 2002 alh 5 speed wagon into a 2002 2.0 auto. Have everything done other than 109 relay and glow plug harness. Would be greatly appreciated man. Email is chevyfan196@yahoo.com

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It's been quite a while since I did that project and will have to search to find the notes/diagrams.
Have you swapped out the instrument cluster and had the immobilizer deleted? That will need to be done also.
Both sides of the ECU wiring harness transferred over into the "new" chassis from the original?
I will do some looking into finding the wiring diagram and pin out change instructions I used. It was relatively easy.

jettawreck said:

It's been quite a while since I did that project and will have to search to find the notes/diagrams.
Have you swapped out the instrument cluster and had the immobilizer deleted? That will need to be done also.
Both sides of the ECU wiring harness transferred over into the "new" chassis from the original?
I will do some looking into finding the wiring diagram and pin out change instructions I used. It was relatively easy.

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Yes I have ecu and all under hood wiring swapped over and hooked up and cluster is ready to go in but I have not got the immobilizer deleted yet. What is best way to get immobilizer deleted? Debated on swapping ignition over so I wouldn't have to delete it but would prefer to just get it deleted if it's not much of a hassle. I definitely appreciate the help.

Alhguy96 said:

Yes I have ecu and all under hood wiring swapped over and hooked up and cluster is ready to go in but I have not got the immobilizer deleted yet. What is best way to get immobilizer deleted? Debated on swapping ignition over so I wouldn't have to delete it but would prefer to just get it deleted if it's not much of a hassle. I definitely appreciate the help.

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I sent mine to a guy that was in MN that deleted the immobilizer. With just a simple immobilizer you end up with a continual flashing immobilizer "warning light". To eliminate that (if it bothers you) you will need to also get the cluster matched or whatever to the deleted ECU. I waited to see if thing would actually work before spending the extra money and now probably never will.
There are members on the forum here that do ECU and cluster pairing and/or immobilizer deletes. "jetta,97" is one that comes to mind.
I will have some more time the next day or so to find the diagram and sub-harness detail.

Edit:
Email with diagram and (limited) info sent!!

jettawreck said:

Email with diagram and (limited) info sent!!

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Would you mind either posting the diagram and info to this thread, or send it to me? kwfiggatt@yahoo.com

I have a very tired 02 TDI that has ~550k miles on it that dropped a valve seat and broke a valve about a month ago. I had already bought a really nice junkyard engine to replace it when a friend offered me a free 03 2.0 golf with a bad tranny that is in MUCH better shape than mine. So now, I'm researching tdi swaps...

Thanks,

Kevin