Rich running D-Jet |
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Rich running D-Jet |
biggy72 |
Jul 24 2011, 10:59 PM
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#1
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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. |
larss |
Jul 24 2011, 11:10 PM
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#2
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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 |
biggy72 |
Jul 24 2011, 11:11 PM
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#3
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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.
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sean_v8_914 |
Jul 25 2011, 07:19 AM
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#4
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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 |
TheCabinetmaker |
Jul 25 2011, 07:52 AM
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#5
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I drive my car everyday Group: Members Posts: 8,301 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.
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reharvey |
Jul 25 2011, 07:54 AM
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#6
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Senior Member Group: Members Posts: 573 Joined: 16-July 08 From: N. E. Ohio Member No.: 9,308 Region Association: North East States |
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biggy72 |
Jul 25 2011, 04:24 PM
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#7
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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. |
TheCabinetmaker |
Jul 25 2011, 04:41 PM
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#8
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I drive my car everyday Group: Members Posts: 8,301 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?
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biggy72 |
Jul 25 2011, 05:00 PM
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#9
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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.
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TheCabinetmaker |
Jul 25 2011, 05:18 PM
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#10
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I drive my car everyday Group: Members Posts: 8,301 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.
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luskesq |
Jul 25 2011, 05:58 PM
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#11
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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 |
914_teener |
Jul 26 2011, 09:01 AM
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#12
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914 Guru Group: Members Posts: 5,201 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern 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 (IMG:style_emoticons/default/WTF.gif) (IMG:style_emoticons/default/WTF.gif) It is? How do you know that? Just wondering. |
luskesq |
Jul 26 2011, 10:43 AM
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#13
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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 (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 |
brenz |
Jul 26 2011, 11:03 AM
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#14
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Member Group: Members Posts: 56 Joined: 10-March 10 From: Delaware, USA Member No.: 11,451 Region Association: MidAtlantic Region |
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. |
biggy72 |
Jul 26 2011, 11:25 AM
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#15
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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. |
biggy72 |
Jul 26 2011, 06:18 PM
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#16
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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.
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biggy72 |
Jul 26 2011, 10:55 PM
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#17
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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. |
TAP |
Jul 27 2011, 07:21 AM
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#18
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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 |
biggy72 |
Jul 27 2011, 09:15 AM
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#19
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Member Group: Members Posts: 209 Joined: 14-January 06 From: Olympia, WA Member No.: 5,418 Region Association: Pacific Northwest |
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. |
TAP |
Jul 27 2011, 09:26 AM
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#20
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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 |
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