UPDATED!: HELP! Lawnmower noise and what looks like backfire in the engine bay, Can someone help me figure out what may have happened? Options

[chrisdaun]

Your symptons are very similar to mine when the CHT harness wire was broken and making intermittent connection.

Check the resistance on the CHT on the CHT lead, then check it through the FI wiring harness at the ECU connector. Wiggle the wires when testing and see if the resistance changes.

My lead was broken on the harness side just before the CHT connector.

Yesterday I took a look in the engine bay and found the vacuum hose had fallen off the MPS. I hooked it back up and the car strated right up, idled great and ran strong. I took her for a drive and she died on me again. This time when trying to start it just cranked and this time I had a puddle of fuel under the tailpipe. This is consistant with what you guys have said for a failing CHT and I have seen this described in other posts as related to the CHT.

I ohmed the CHT last night while the engine was still hot and got a reading of 132 at the CHT plug. The PO installed a 270 ohm resister in line with the CHT so i took it off and will test the CHT connection at the ECU plug tonight.

Does anyone know why the PO whould have added to 270 ohm resister to the CHT?

Also, after taking off the resister the car ran and no more gas in the exhaust but now it idles up and down and almost dies.

[Dave_Darling]

That's a factory part for the 73 2.0 system.

Double-check that MPS hose....

--DD

[McMark]

Change out the CHT. They're not particularly expensive and if you are getting erratic running issues it's a cheap thing to try. I had a 912E (same engine) that ran great most of the time but would occasionally just stop. I checked the CHT multiple times and it looked fine, but after swapping it out, no more problems. And once I had the old CHT out I could easily confirm it was dead.

This sounds like exactly what's going on with yours.

[JFJ914]

Change out the CHT. They're not particularly expensive and if you are getting erratic running issues it's a cheap thing to try. I had a 912E (same engine) that ran great most of the time but would occasionally just stop. I checked the CHT multiple times and it looked fine, but after swapping it out, no more problems. And once I had the old CHT out I could easily confirm it was dead.

This sounds like exactly what's going on with yours.

The only problem I see with buying a new one is that you'll have some time finding a -017 CHT. The -012 is usually availible but it's not compatible with the '73 1.7/2.0 ECU.

[chrisdaun]

Change out the CHT. They're not particularly expensive and if you are getting erratic running issues it's a cheap thing to try. I had a 912E (same engine) that ran great most of the time but would occasionally just stop. I checked the CHT multiple times and it looked fine, but after swapping it out, no more problems. And once I had the old CHT out I could easily confirm it was dead.

This sounds like exactly what's going on with yours.

I've got a '71 that the PO upgraded to a 2.0L (not sure of the year) and the post above
shows that I have a factory part from a '73 2.0L. Pelicanparts stocks the CHT but specifically excludes the '73 2.0L model. Any advice on this? What is the difference and am I out of luck getting a new CHT if I do indeed have a '73 2.0L in the car?

http://www.pelicanparts.com/cgi-bin/smart/...29%2C%20Each%20

[McMark]

The wrong new one is going to be 'righter' than the broken one. (IMG:style_emoticons/default/wink.gif)

Brad Anders (D-Jet guru) says on his tech page that there shouldn't be a significant difference.

Remember the CHT is only for warmup. Once the engine is hot is basically does nothing. So even a brand new 'wrong' CHT will be right at operating temp.

[chrisdaun]

The wrong new one is going to be 'righter' than the broken one. (IMG:style_emoticons/default/wink.gif)

Brad Anders (D-Jet guru) says on his tech page that there shouldn't be a significant difference.

Remember the CHT is only for warmup. Once the engine is hot is basically does nothing. So even a brand new 'wrong' CHT will be right at operating temp.

I might have some good news! I pulled the ECU and according to Brad Anders' page my ECU is from a '74. Part#: [0 280 000 044], [039 906 021]

Looks like i'm good to order a new CHT sensor from Pelican.

I did also notice that my distributor has a vacuum line on it that the Haynes manual shows should go back to the throttle body but my throttle body only has one stub for a vacuum hose and its already got the green vacuum line from the bottom of the distributor connected to it. Any ideas on if this is OK to leave as is? Or do i need to cap/T this in somewhere? See picture below the ECU picture below.

Thanks again for everyone's help with this. Its been a good learning experience so far! (IMG:style_emoticons/default/biggrin.gif)

[euro911]

Check out the hose diagrams on Pelican ... one of them should be right for your system.

CLICK HERE

[Dave_Darling]

If there is no fitting on the throttle body for the advance line, leave the line disconnected. Just like it is now. Many 74+ 914s didn't have vacuum advance at all.

--DD

[chrisdaun]

The wrong new one is going to be 'righter' than the broken one. (IMG:style_emoticons/default/wink.gif)

Brad Anders (D-Jet guru) says on his tech page that there shouldn't be a significant difference.

Remember the CHT is only for warmup. Once the engine is hot is basically does nothing. So even a brand new 'wrong' CHT will be right at operating temp.

So I replaced the CHT and when I was removing the old one i found that it wasnt even hand tight. It must have loosened up over time but since I already had a new one, I replaced it.

After putting in the new CHT the car fired right up and idled really smooth but as soon as the engine started to heat up, the idle got really bad and the car would die. starting it and keeping my foot on the gas shook the car extremely bad so I put the 270ohm resister back inline with the new CHT and this seemed to fix that problem.

I took the car out for a nice long drive because the engine was idling great again and about 15 minutes later the car started to choke and it died again with a strong smell of fuel. So replacing the CHT didnt fix my problem. (IMG:style_emoticons/default/mad.gif)

After the car dies like this it just cranks and cranks. But the last time if i held the gas peddle down and cranked it for a good 30 seconds it fired up but would not stay running unless i kept on the gas and revved it above 2500RPM.

After the car cools down it seems to be OK again. Failing fuel pump? What should I check next?

[Scott S]

My car did this exact same thing several years ago. It was finally sourced to an extremely frayed ground wire in the bottom of my distributor (only 2-3 strands were still making a connection). The car would fire right up and drive great when cold - then start running like crap and eventually die. once it cooled off, if would start right up again. I was sure it was fuel related. But once the wire was fixed, I never had the issue again. Its been 15 years.

Sorry for the out of left field idea.....

[Jon H.]

Check to see if you have compression. If you don't have compression on that one cylinder it will flood and then not fire which would result in the fuel your seeing. I had the same problem with my westfalia. With a dead cylinder it would always fire right up and then run poor once warm and then would not start after stalling. You should perform a leaqk down test. If you don't have the tools one quick and red neck method is to start the engine after it has cooled off and very quickly feel the exhaust right at the cylinder if it isn't even warm then that cylinder is pooched. You could have burnt your exhaust valve.

Regards'

Jon

[euro911]

There's a real easy method to find a dead cylinder ... pull the plug wire for a cylinder (one at a time) and if the RPM doesn't drop, you've found it.

[Jon H.]

There's a real easy method to find a dead cylinder ... pull the plug wire for a cylinder (one at a time) and if the RPM doesn't drop, you've found it.

Thats not nearly as fun as burning your fingers (IMG:style_emoticons/default/smile.gif)

[euro911]

True ... (IMG:style_emoticons/default/smoke.gif)

[Rod]

I also had a similar problem to yours and was traced back to dodgy injector connections, which only manifested themselves when hot - when it's playing up wiggle the injector electrical connectors a little, one at a time.... It may just fire into life...

A bowlsby engine bay loom fixed my electrical problems for good..

[chrisdaun]

There's a real easy method to find a dead cylinder ... pull the plug wire for a cylinder (one at a time) and if the RPM doesn't drop, you've found it.

I tried this today and the RPMs dropped when unplugging each spark plug wire from the plug individually.

I'll have to keep digging... Wish I had more time to troubleshoot this thing.

Thanks again to everyone for all the great help and direction! You guys are the best (IMG:style_emoticons/default/biggrin.gif)