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Posted by: biggy72 Jul 24 2011, 10:59 PM

So I just got my 72 1.7 liter D-Jet back on the road. It's been running rich since I got it going again, and the other day it was rich enough to foul out two plugs. I haven't changed my fuel pressure yet, but it's set at 31 psi. I think it's supposed to be down around 28 or 29, but is that enough of a difference to cause that much change in how rich the engine is running?

I'm going to go through piece by piece tomorrow checking for vacuum leaks. I unplugged the cold start valve and it didn't make a difference, but I haven't pulled it out yet to see if it's leaking at all.

I'm going to go right down the list: http://members.rennlist.com/pbanders/DJetParts.htm

But I wasn't sure if the fuel pressure issue could be enough to cause the entire problem.

Posted by: larss Jul 24 2011, 11:10 PM

No, that small difference in pressure is not likely to cause the problem. Yes its a good idea to follow the superb pbanders site, it will lead you to the solution.
I would check the MPS first.


/Lars S

Posted by: biggy72 Jul 24 2011, 11:11 PM

Already did. I have two and both hold a vacuum.

Posted by: sean_v8_914 Jul 25 2011, 07:19 AM

dirty cht connection?
or

vacuum leak so severe thayt the MPS sees les vac thinking its at more load than it really is

Posted by: vsg914 Jul 25 2011, 07:52 AM

Cht, or mps is the usual culprits for rich run. The cold start valve can stick open feeding fuel directly into the plenum. Remove and plug the hose to test.

Posted by: reharvey Jul 25 2011, 07:54 AM

Posted by: biggy72 Jul 25 2011, 04:24 PM

I haven't had a chance to go down my list yet, but I've been wondering about my engine. I bought it used from another guy and it seems to run really well. The problem is that I have no idea what cam it has in it. If it has a big cam this could be my problem and I suspect I could test the manifold pressure to see if it's close to being correct.

Does anyone have values for what it should be at for a few different rpms? Is this a good way to check? If so I'll pick up a vaccum gauge to check.

Either way I'll start on my list of things to check tonight after work.

Posted by: vsg914 Jul 25 2011, 04:41 PM

If it has fuel injection, it doesnt have a big cam. Why do you think it does?

Posted by: biggy72 Jul 25 2011, 05:00 PM

I bought the long block from someone in Spokane, then pieced together my djet from the original engine/another setup I bought from someone else. I know my djet parts are correct per Pbanders sight, but I don't know much about the engine.

Posted by: vsg914 Jul 25 2011, 05:18 PM

Ok, I understand why you dont know whats inside, but the fact that it runs good would susgest a stockish cam. D jet just doesnt have the capabilities of being tuned much differently.

Posted by: luskesq Jul 25 2011, 05:58 PM

Don't know about a '72 but my '70 cold start valve is directional. After I got my car it took a while to figure out that someone before me installed the valve 180 degrees off. Reversed it and no more rich startup.

Keith

Posted by: 914_teener Jul 26 2011, 09:01 AM

It is? How do you know that?

Just wondering.

Posted by: luskesq Jul 26 2011, 10:43 AM

Said so in Haynes and if you look on the valve it has a directional arrow. Don't recall which direction it should point but Haynes provides that answer. It would be easy to install 180 off if you don't pay attention. Made a huge difference in richness. If you can't find it in Haynes, I'll see if I can find it.

keith

Posted by: brenz Jul 26 2011, 11:03 AM

I’ve been through a similar problem. Not knowing if you have a stock cam throws off everything. You need to tee in a vacuum gauge between your mps and the plenum. You should have 15”hg at 900 rpm and the needle should be steady. Vacuum should increase/decrease with rpm changes but should hit the mark at 900 rpm.

I see 6”hg at 1100 rpm. See my post "Vacuum Leak?" for any clues. Mine idles but exhaust is punchy/lumpy like a motorcycle. Rich as hell. But driving, especially above 2500 rpm it’s great. So much torque. It belongs on a track.

You mentioned fouling 2 plugs. Were the other 2 clean? Check your trigger points just to be sure. Also, you can check if all cylinders are firing by quickly touching each exhaust header after running it for half a minute or so. Don't burn your hand.

Post back with your vacuum readings and we’ll keep going.

Posted by: biggy72 Jul 26 2011, 11:25 AM

My dad came over last night so I didn't have much time to work on anything, but I did check my head temp sensor against pbanders sight and I had 3.15 kohms at about 65°F which seems about right.

Yes the two plugs were badly fouled, the other two did look surprisingly good. I can't quite remember, but it does seem like the front two plugs that were fouled. I'll check the cold start valve direction when I get a chance and I'll buy a vacuum gauge either tonight or tomorrow night.

Posted by: biggy72 Jul 26 2011, 06:18 PM

I just checked and my cold start valve is indeed backwards. I'll swap it around in a few and see how it goes. I still need to get a vacuum gauge and then I'll be doing that too even if I think it's running correctly just so I know for sure.

Posted by: biggy72 Jul 26 2011, 10:55 PM

I pulled the cold start valve out and put it in a jar to see if it was leaking anything while the fuel pump was running. Even though it was in backwards, nothing came out. I've had the harness unplugged from it for awhile so I don't think that was the problem.

I picked up a vacuum gauge tonight, so I'll test that tomorrow.

Posted by: TAP Jul 27 2011, 07:21 AM

You need to put some heat to the CHT and see if the values change, should decrease. If not, it will cause the ECU to see the engine as cold and give a rich mixture.
Tom

Posted by: biggy72 Jul 27 2011, 09:15 AM

In order to do this I'm thinking just run the engine for a few minutes and then shut it off and recheck the resistance? I haven't really looked, how hard is it to pull the head temp sensor? I don't really think this is the problem because it's running rich even when first started, but I'll double check it anyway.

Posted by: TAP Jul 27 2011, 09:26 AM

Yes,
Just run it for a few minutes and then check the CHT resistance. If it is less, that is what you would be looking for.
Already running rich at start-up? I don't know what may be causing that. Leaky injectors? Might be a good idea to check the injectors for the plugs that fouled.
Tom

Posted by: brenz Jul 27 2011, 10:24 AM

You don't need to pull the CHT to check the resistance. It grounds on the engine case. Only pull it if it checks out bad. It's probably fine though.

Make sure all cylinders are firing. If it's trigger points it would be 2,3 or 1,4. Which plugs are clean and which are fouled?

Injectors for the clean plugs might not be firing or the injectors for the fouled plugs could be leaking. Check your wiring if you didn't already. Then pull out the injectors from the head but leave them connected to the fuel line. Put them in glass jars and run the pump. They should squirt a little fuel. If one or more doesn't or if one or more leak, get them cleaned.

Posted by: biggy72 Jul 28 2011, 10:23 PM

My CHT resistance is going down as it gets warmer. I checked my vacuum and it looks like I'm pulling close to 15 psi at around 900 rpm. Cylinders 1 and 4 are not nearly as warm as 2 and 3. Does this signal a trigger point problem? I haven't pulled my injectors to check them yet, but a trigger point problem will show up in the injectors too so.... if the cylinders indicate a problem with them I'll work on that first.

Posted by: biggy72 Jul 28 2011, 11:08 PM

Well it looks like my brand new distributor cap has loose terminals for 3 out of the 4 plugs. They spun in place and the rotor started grinding into them. Hopefully a new cap and rotor will fix this, and hopefully with a little complaining I should get them for free since this engine has all of about an hour on it since the new cap and rotor went on. The cap even says "MADE IN THE USA" inside of it..... guess I should have gotten a Chinese one.

Posted by: vsg914 Jul 29 2011, 04:14 AM

Buy a bosch cap and rotor.

remove trigger points, clean, relube, and reinstall. They fire in pairs. 1&4, 3&2.

Posted by: biggy72 Jul 29 2011, 07:15 AM

I've got a petronix setup, but it was definitely dirty in there from all of the grinding....

Posted by: Bartlett 914 Jul 29 2011, 03:18 PM

Don't confuse the pertronics with the trigger points. These are different animals in the distributor

Posted by: biggy72 Jul 29 2011, 03:26 PM

Oh ok, thought you were talking about the points. I won't be able touch it until Sunday night, but I should be able to go through everything pretty quickly.

What kind of lube do you suggest for the trigger points? Regular grease? dielectric grease? some other special lube?

Posted by: Dave_Darling Jul 29 2011, 04:54 PM

Bosch distributor grease on the rubbing blocks, where they ride on the cam. Just like regular points get.

One tube of Bosch distributor grease will last you a lifetime. More than one lifetime, if you've got a Pertronix in your car.

All of your favorite Porsche parts places will carry it.

--DD

Posted by: jcd914 Jul 29 2011, 11:01 PM

This has always been my problem with electronic ignition in 914's.
Once the electronics are installed and the ignition points don't need maintenance people tend to forget that there are other parts of the distributor that do still need maintenance.
At a tune-up I would pull the distributor and clean and lube the advance weights, apply oil to the felt button under the rotor and clean and lube the FI points. Add a new distributor o-ring and put it back in. If our Sun distributor machine was working I would check the advance and set the dwell while the distributor was out.
Customers that had an added in electronic ignition, seldom wanted to pay for distributor servicing since "it doesn't have points anymore".

Jim

Posted by: Prospectfarms Jul 30 2011, 05:40 AM

OT ? : jcd914, I assume you pulled the distributors to replace points, along with performing the testing and lube you just described, and then timed those motors after reinstalling the distributor?

I dislike pulling my dizzy 'cause re- timing the ignition takes three hands on my 1.7. To pull it, I have to turn the dizzy to access the retaining nut underneath the advance can--ruining my hard-won timing.

Now it's time to freshen up those injector points, so I'm wondering if you recall any procedures that served to save time (so to speak) during the dizzy remove/motor tune-up process, back when you were pulling all those distributors?

Posted by: jcd914 Jul 30 2011, 12:00 PM

I use a 13mm distributor wrench to reach under the advance and loosen the nut holding the distributor bracket to the case. Then I use my finger tips to remove the nut and washers so I can pull out the distributor. This keeps the timing close to where it was when the dist goes back in but I always checked and adjusted the timing after.

You have to pull the distributor to remove the FI trigger points which need to be cleaned and lubed anyway. So it was just a standard routine for me. Pull the dist and take care of everything at once. Replacing the ignition points only adds 5 minutes or so to the whole process.

Jim

Posted by: biggy72 Aug 1 2011, 11:51 PM

I figured it out finally. Replaced the cap and rotor because of the above problems. Still had a miss on 1 and 4 so I pulled the distributor out and checked continuity on the trigger points while I spun the shaft. One of the side was working, the other side was not. I pulled it apart and cleaned everything really well, checked everything by hand and it all looked ok. Put it back in and still had the same issue. I tried moving the trigger points around side to side and then retightening and that didn't help either.

So I pulled out my spare distributor that's pretty cruddy inside and cleaned those trigger points and then reinstalled them in my better distributor. After setting the timing we're back on all 4 cylinders. I should probably get a new set just in case I have another problem. Does anyone make them new?

Posted by: biggy72 Aug 2 2011, 12:16 AM

Has anyone tried getting one of these remanufactured distributors?

https://www.napaonline.com/Catalog/CatalogItemDetail.aspx?A=NRD48915_0271598799&An=599001+101972+50062+2062020

I see AA has trigger points for $202 and was thinking a nice remanufactured distributor might be a better solution if it's that cheap.

Posted by: Prospectfarms Aug 2 2011, 08:50 AM

Thanks for that information. Answered my question.

Sounds like Biggy72 has solved his engine problem. As far as reliability of NAPA rebuilt distributor, there seems to be a consensus that the commonly available rebuilt dizzy's are not a good value. You should ask NAPA who does their work. There are folks on this board and at the SAMBA that have excellent reputations for rebuilding dizzy's, perhaps they might have a good source for the points. I have no personal experience beyond taking my unit apart and cleaning it two months ago (and forgetting to clean and lubricate the injector points!)