 D jetronic problems |
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| Edchina |
 Mar 25 2013, 01:30 PM
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#1
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Newbie  Group: Members Posts: 17 Joined: 18-March 13 From: Bremen/New Orleans Member No.: 15,665 Region Association: None  |
Hi,
I have been troubleshooting the D jetronic on my 914-4 1975, 2 liter engine. Bought a fine car, but the previous owners messed the D jetronic system up. Vacuum hoses were missing, throttle switch was new but not adjusted, fuel lines clogged up and temperature sensors not connected. Here is what I have done so far: -Overhauled fuel tank. -Installed new fuel pump and filter. -Checked fuel pressure at the regulator (2 bar) -Changed all vacuum hoses (no leaks) -Adjusted valves -Checked trigger contacts (looked like new) -Checked dwell angle (46 deg.) and breaker points -Adjusted timing -Adjusted throttle switch -Compression test showed 121 Psi on all cylinders -Installed new pressure sensor after the old one failed during vacuum test (membrane cracked) -checked electric system with Bosch tester -checked electric system manually Problem: Engine is running rich and the idle is high (around 1200 RPM). By installing a vacuum gage between pressure Manifold and pressure sensor the vacuum changes (-0.65 ~ -0.5 Bar) rather than being constant. Adjusting the bypass screw at the trottle does not change the idle much. The CO value is around 4% and does not change much when adjusting the potentiometer at the control unit. My question is what is causing the vacuum to rise and fall causing the RPM's to increase and decrease by 400 RPM. Thanks |
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Replies
| Edchina |
Mar 25 2013, 02:55 PM
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#2
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Newbie Group: Members Posts: 17 Joined: 18-March 13 From: Bremen/New Orleans Member No.: 15,665 Region Association: None |
-Changed the seals for all injectors
-Pressure sensor is new On this car the deacceleration valve is missing. I have a new cylinder head temperature sensor, but would have to make a tool to insert it. I am also thinking about the intake runer hoses causing a leak. |
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| falconfp2001 |
Mar 25 2013, 05:17 PM
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#3
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Pancho Pantera Group: Members Posts: 451 Joined: 5-December 10 From: Downey, CA Member No.: 12,456 Region Association: Southwest Region |
QUOTE(Edchina @ Mar 25 2013, 01:55 PM)  -Changed the seals for all injectors -Pressure sensor is new On this car the deacceleration valve is missing. I have a new cylinder head temperature sensor, but would have to make a tool to insert it. I am also thinking about the intake runer hoses causing a leak. All you need is a cheap long 13mm socket then cut a slot in it so you can keep from damaging the wire. All is takes is a grinder and some time. You don't necessarily need the Deceleration valve to have the D-Jet run well but it does keep you from backfiring like crazy. They tend to get sticky after so many years so I just removed mine when I had D-Jet and it would just pop some while decelerating. No real big backfires unless you step on it a lot. |
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| mepstein |
Mar 25 2013, 05:29 PM
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#4
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914-6 GT in waiting Group: Members Posts: 19,649 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region 
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QUOTE(falconfp2001 @ Mar 25 2013, 07:17 PM) QUOTE(Edchina @ Mar 25 2013, 01:55 PM) -Changed the seals for all injectors -Pressure sensor is new On this car the deacceleration valve is missing. I have a new cylinder head temperature sensor, but would have to make a tool to insert it. I am also thinking about the intake runer hoses causing a leak. All you need is a cheap long 13mm socket then cut a slot in it so you can keep from damaging the wire. All is takes is a grinder and some time. * No need to cut a notch! All you need to do is buy a deep socket ($5) and bunch the wire inside the socket. Done. |
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Posts in this topic
Edchina D jetronic problems Mar 25 2013, 01:30 PM
The Cabinetmaker A hunting idle is caused a lean condition. You mus... Mar 25 2013, 01:46 PM Edchina Yes, the vacuum hose was disconnected from the vac... Mar 25 2013, 02:42 PM 76-914 What Curt said :agree: Also, you bought a new MAP ... Mar 25 2013, 02:47 PM JawjaPorsche If the intake hoses are 40 years old, they probabl... Mar 25 2013, 03:20 PM r_towle Have you cleaned and tested the Throttle Control S... Mar 25 2013, 06:04 PM Edchina The throttle switch was brand new. Just wasn't... Mar 25 2013, 06:45 PM Dave_Darling High idle == vacuum leak or advanced timing.
Most... Mar 25 2013, 09:27 PM The Cabinetmaker Where did you get this new tps? Was it a new unit?... Mar 26 2013, 04:34 AM
Edchina
Where did you get this new tps? Was it a new unit... Mar 26 2013, 12:12 PM 76-914 You have a NEW MPS? If so, nice find. If it's ... Mar 26 2013, 08:49 AM Edchina I bought it in Germany at a Volkswagen dealer for ... Mar 26 2013, 12:07 PM The Cabinetmaker Pardon me if I missed it, but has it been adjusted... Mar 26 2013, 04:16 PM Edchina
Pardon me if I missed it, but has it been adjuste... Mar 26 2013, 05:27 PM The Cabinetmaker Ok, have you tried unpluggingthe tps? It will actu... Mar 26 2013, 06:31 PM |
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