D-Jet Conversion not going as planned., Car starts but will not run. Options

[slapshot]

I am converting back to D-Jet and my car will start but dies right after. It will not rev up applying throttle. I have a 1975 914 2.0. It was running great with Weber 40s prior.

The D-Jet system is from a 1974 2.0. All the parts came in visibly good condition. TPS calibrates good, AAV tested good, Thermo sensor good, air intake temp sensor good, and a new cylinder head temp sensor. The only test that I think is failing is the vacuum test on the MPS. It leaks. Video of testing the MPS.. The MPS has also been rebuilt at some point. The original part # has been removed. There's a good chance it is not calibrated for my car. I have all new vacuum hose and fuel pressure is between 28 and 30.

I don't have any tools to calibrate the MPS. Should I try turning the inner screw on the MPS to see if it helps? Or should I send it to someone to have it rebuild again and recalibrated? If the later do you have any recommendations on who to send it to?

[fiacra]

Not the person to ask about how to calibrate your MPS, but if you are looking to have it rebuilt, or to buy a rebuilt MPS:

Jeff Bowlsby:

https://bowlsby.net/914/WiringHarnesses/#Miscellaneous

Auto Atlanta:

http://www.autoatlanta.com/Porsche-Rebuilt...B039906051.html

Tangerine Racing sells a repair/calibration kit, but the website shows the diaphragm as being out of stock right now.

There are probably other vendors, but that's what comes to mind right now.

Good luck!

[JeffBowlsby]

Try manually pumping the MPS up to 15 inHg and starting the engine. If it starts, try to keep it pumped up to 15. Those should be idle conditions.

[JeffBowlsby]

dbl post

[slapshot]

Not the person to ask about how to calibrate your MPS, but if you are looking to have it rebuilt, or to buy a rebuilt MPS:

Jeff Bowlsby:

https://bowlsby.net/914/WiringHarnesses/#Miscellaneous

Auto Atlanta:

http://www.autoatlanta.com/Porsche-Rebuilt...B039906051.html

Tangerine Racing sells a repair/calibration kit, but the website shows the diaphragm as being out of stock right now.

There are probably other vendors, but that's what comes to mind right now.

Good luck!

Looking at the parts from Tangerine, it looks like the parts in mine. I have that brass diaphragm and the black cap on the outer adjustment hole. It might be the kit they used (IMG:style_emoticons/default/confused24.gif).

Thanks for those options, if nothing else I will need to pickup one of those rebuilt ones.

[slapshot]

Try manually pumping the MPS up to 15 inHg and starting the engine. If it starts, try to keep it pumped up to 15. Those should be idle conditions.

I gave that a shot and with 15 inHg it would not turn over at all. I put the vacuum hose back on and it cranks over buts dies quickly. Seem like as vacuum increases it has a problem running.

[Craigers17]

I’m sure you’ve already checked this off on your troubleshooting list, but were you using the 123 distributor when it was carb’d? If so, was it the same one? I could be wrong, but I was thinking that the D-jet one was different from the carb’d version. Could be another thing to look at.

[JeffBowlsby]

Post a photo of how the 123 wires are installed to the
FI harness connector please.

[slapshot]

I’m sure you’ve already checked this off on your troubleshooting list, but were you using the 123 distributor when it was carb’d? If so, was it the same one? I could be wrong, but I was thinking that the D-jet one was different from the carb’d version. Could be another thing to look at.

It is the same. I bought the D-Jet version because I planned on switching back. I asked when I purchased the distributor and he said the D-Jet one will work with carbs and I had no issue setting it up with mine. The 123 distributor is awesome.

[slapshot]

Here's a pic and a pic of the diagram from what I followed off of 123's website

[Robarabian]

Easy Supplier with warranty as well:

https://fuelinjectioncorp.com

Not the person to ask about how to calibrate your MPS, but if you are looking to have it rebuilt, or to buy a rebuilt MPS:

Jeff Bowlsby:

https://bowlsby.net/914/WiringHarnesses/#Miscellaneous

Auto Atlanta:

http://www.autoatlanta.com/Porsche-Rebuilt...B039906051.html

Tangerine Racing sells a repair/calibration kit, but the website shows the diaphragm as being out of stock right now.

There are probably other vendors, but that's what comes to mind right now.

Good luck!

[TheCabinetmaker]

Do you hear the fuel pump come on for a half second when you turn the key to "on"? That primes the pump so you can start it. As soon as it's running, the ECU takes over to provide power to the pump. It's connected by a fuse and relays on the relay board. It's very rare, but ECUs do fail!

[JeffBowlsby]

Thx, that’s trigger points connection and looks wired correctly.

[slapshot]

Do you hear the fuel pump come on for a half second when you turn the key to "on"? That primes the pump so you can start it. As soon as it's running, the ECU takes over to provide power to the pump. It's connected by a fuse and relays on the relay board. It's very rare, but ECUs do fail!

I do hear the pump for a second with key on before I crank it. The fuel pressure is 28 before crank and 31 during and while its sputtering before it dies. Then drops back to 28.

[JeffBowlsby]

Are you getting spark at the plugs?

Injectors verified to fire…recent cleaning and flow test?

[emerygt350]

Can you keep it running with starter fluid?

[JamesM]

I am converting back to D-Jet and my car will start but dies right after. It will not rev up applying throttle. I have a 1975 914 2.0. It was running great with Weber 40s prior.

The D-Jet system is from a 1974 2.0. All the parts came in visibly good condition. TPS calibrates good, AAV tested good, Thermo sensor good, air intake temp sensor good, and a new cylinder head temp sensor. The only test that I think is failing is the vacuum test on the MPS. It leaks. Video of testing the MPS.. The MPS has also been rebuilt at some point. The original part # has been removed. There's a good chance it is not calibrated for my car. I have all new vacuum hose and fuel pressure is between 28 and 30.

I don't have any tools to calibrate the MPS. Should I try turning the inner screw on the MPS to see if it helps? Or should I send it to someone to have it rebuild again and recalibrated? If the later do you have any recommendations on who to send it to?

The MPS is one of the most critical components of the system, if not the MOST critical to have correct and working. That being said the leak in you have in the video shouldnt be enough to cause the behavior you are describing. Of course not having a critical leak doesn't guarantee its not still bad, mismatched, or miscalibrated. It would be helpfull to hear what it sounds like when attempting and failing to rev but a couple things come to mind:


First, A rebuilt MPS with the numbers ground off is absolutely suspect. I would suggest you are just chasing your tail until you have confirmed you have a known good, matched MPS. Also while these are not incredibly difficult to "rebuild" the ONLY way to properly calibrate them is with a good matching MPS in hand to clone the adjustment with and I wouldn't assume whoever rebuilt it did it correctly, likely the opposite. Setting the inductance values based off numbers someone else gives you will at best get them in the ballpark, but most likely wont be correct.

Second, what is the advance curve you have set on the 123dizzy?

You said it will start but not hold idle and die. Is this without stepping on the gas at all or do you have to floor it? does flooring it prevent it from dying once started?

Sputtering and starting only when floored and not revving could be a sign of a broken connection to the head temp sensor as well. I would absolutely start with the MPS but if you get past that you may want to check continuity of the CHT end to end, starting with the CHT pin at the ECU connector though to the engine block.

[slapshot]

Are you getting spark at the plugs?

Injectors verified to fire…recent cleaning and flow test?

The car does start fairly quickly when cranking but sputters and dies a second or two after I stop cranking. I haven't verified all plugs are still sparking. This was a good running car with carbs. No change to the plug, wires and distributor with this switch to FI.

I did test the injectors, except the cold start. All had good flow on the bench. I have not done a flow test. I'm thinking of pulling them and putting them in jars and crank it for about 30 seconds and see how each do.

[slapshot]

Can you keep it running with starter fluid?

I tried that and starting fluid seemed to flood it and it made it harder to turn over.

[emerygt350]

That is very strange. Have you checked the oil? Is it gassy? My d-jet will idle with the mps vacuum hose disconnected. Hell, you can drive it like that too but it's awful. I am wondering about the cht. Check the resistance on that.