Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG. This site is not affiliated with Porsche in any way.
Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners.
 

Welcome Guest ( Log In | Register )

2 Pages V  1 2 >  
 Reply to this topicStart new topic
> Rich running D-Jet
biggy72
post Jul 24 2011, 10:59 PM
Post #1


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
larss
post Jul 24 2011, 11:10 PM
Post #2


Member
**

Group: Members
Posts: 428
Joined: 10-September 09
From: Sweden
Member No.: 10,787
Region Association: Scandinavia
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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
biggy72
post Jul 24 2011, 11:11 PM
Post #3


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
Already did. I have two and both hold a vacuum.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
sean_v8_914
post Jul 25 2011, 07:19 AM
Post #4


Chingon 601
****

Group: Members
Posts: 4,011
Joined: 1-February 05
From: San Diego
Member No.: 3,541
dirty cht connection?
or

vacuum leak so severe thayt the MPS sees les vac thinking its at more load than it really is
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
TheCabinetmaker
post Jul 25 2011, 07:52 AM
Post #5


I drive my car everyday
*****

Group: Members
Posts: 8,300
Joined: 8-May 03
From: Tulsa, Ok.
Member No.: 666
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
reharvey
post Jul 25 2011, 07:54 AM
Post #6


Senior Member
***

Group: Members
Posts: 573
Joined: 16-July 08
From: N. E. Ohio
Member No.: 9,308
Region Association: North East States
(IMG:style_emoticons/default/agree.gif)
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
biggy72
post Jul 25 2011, 04:24 PM
Post #7


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
TheCabinetmaker
post Jul 25 2011, 04:41 PM
Post #8


I drive my car everyday
*****

Group: Members
Posts: 8,300
Joined: 8-May 03
From: Tulsa, Ok.
Member No.: 666
If it has fuel injection, it doesnt have a big cam. Why do you think it does?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
biggy72
post Jul 25 2011, 05:00 PM
Post #9


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
TheCabinetmaker
post Jul 25 2011, 05:18 PM
Post #10


I drive my car everyday
*****

Group: Members
Posts: 8,300
Joined: 8-May 03
From: Tulsa, Ok.
Member No.: 666
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
luskesq
post Jul 25 2011, 05:58 PM
Post #11


Member
**

Group: Members
Posts: 276
Joined: 24-October 10
From: Fresno, CA
Member No.: 12,303
Region Association: Central California
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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
914_teener
post Jul 26 2011, 09:01 AM
Post #12


914 Guru
*****

Group: Members
Posts: 5,197
Joined: 31-August 08
From: So. Cal
Member No.: 9,489
Region Association: Southern California
QUOTE(luskesq @ Jul 25 2011, 04:58 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



(IMG:style_emoticons/default/WTF.gif) (IMG:style_emoticons/default/WTF.gif)

It is? How do you know that?

Just wondering.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
luskesq
post Jul 26 2011, 10:43 AM
Post #13


Member
**

Group: Members
Posts: 276
Joined: 24-October 10
From: Fresno, CA
Member No.: 12,303
Region Association: Central California
QUOTE(914_teener @ Jul 26 2011, 08:01 AM) *

QUOTE(luskesq @ Jul 25 2011, 04:58 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



(IMG:style_emoticons/default/WTF.gif) (IMG:style_emoticons/default/WTF.gif)

It is? How do you know that?

Just wondering.

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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
brenz
post Jul 26 2011, 11:03 AM
Post #14


Member
**

Group: Members
Posts: 56
Joined: 10-March 10
From: Delaware, USA
Member No.: 11,451
Region Association: MidAtlantic Region
QUOTE(biggy72 @ Jul 25 2011, 07:00 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.



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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
biggy72
post Jul 26 2011, 11:25 AM
Post #15


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
biggy72
post Jul 26 2011, 06:18 PM
Post #16


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
biggy72
post Jul 26 2011, 10:55 PM
Post #17


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
TAP
post Jul 27 2011, 07:21 AM
Post #18


Newbie
*

Group: Members
Posts: 10
Joined: 23-July 11
From: Port Orchard, Wa.
Member No.: 13,353
Region Association: None
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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
biggy72
post Jul 27 2011, 09:15 AM
Post #19


Member
**

Group: Members
Posts: 209
Joined: 14-January 06
From: Olympia, WA
Member No.: 5,418
Region Association: Pacific Northwest
QUOTE(TAP @ Jul 27 2011, 06:21 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



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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
TAP
post Jul 27 2011, 09:26 AM
Post #20


Newbie
*

Group: Members
Posts: 10
Joined: 23-July 11
From: Port Orchard, Wa.
Member No.: 13,353
Region Association: None
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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
« Next Oldest · 914World Garage · Next Newest »
 

2 Pages V  1 2 >
Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 

Display Mode: Standard · Switch to: Linear+ · Switch to: Outline

Track this topic · Email this topic · Print this topic · Subscribe to this forum

- Lo-Fi Version Time is now: 16th May 2024 - 07:17 AM
Invision Power Board v9.1.4 © 2024  IPS, Inc.
All rights reserved 914World.com © since 2002
914World.com is the fastest growing online 914 community!
We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ...