Car never ran better - THEN!, Seems when hot there is no low end power |
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Car never ran better - THEN!, Seems when hot there is no low end power |
ctc911ctc |
Jun 25 2023, 04:30 PM
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#1
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Senior Member Group: Members Posts: 893 Joined: 9-June 18 From: boston Member No.: 22,206 Region Association: North East States |
'74 2.0 - 25K miles
It has been a very long journey. I, with my 17yr old son who is now 21, rebuilt nearly every system including the Engine and Transmission (a nod to Dr. Evil !! ). My son and I have learned a great deal, however, this one has me stumped. The car runs terrific and is strong, smooth and a joy to drive, today I took it around the Lakes here in Arlington MA and at the end of the drive there is a hill with a red light - I caught the red. I waited as the button pushers jaywalked (after they hit the button) and then I waited some more with the crosswalk signs blinking and no one crossing.....sigh OK, there is the green and I ease out the clutch and apply a little gas AND nothing...... nearly idling. I then bury the gas and the car stalls.......and since this is New England everyone starts beeping and yelling - so I get the flashers on and people go around me. I wait another light cycle and get the cars started by pumping the gas and keeping it running over 1500, once it started moving it ran fine. It is almost as if there was zero power below 1500, though when the car was rolling everything worked as you would expect. When the car is cold the low power is as normal as a 90HP engine can be. The temp of the car is about 2/3rds deflection of the center console temp gauge. I am thinking all sorts of complicated thoughts.......head temp sensor is sending weird signals to the Bosch controller OR when super hot the vacuum system starts leaking, etc. So, I thought I would start here - any ideas teeners???? Keep me sane and guide me to the light! CTC911CTC |
914_teener |
Jul 6 2023, 11:35 AM
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#2
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914 Guru Group: Members Posts: 5,205 Joined: 31-August 08 From: So. Cal Member No.: 9,489 Region Association: Southern California |
So assumptions.....starts with ass...
The D-jet system once set...to the stock design is pretty simple. First: You don't wrap the pump in insulation...bad. The pump is cooled by not only the air surrounding it but also by the fuel it pumps. Follow the stock design and use the rubberized stock isolators. That location you already have it in is almost the area I relocated my fuel pump. I ran that car in 120 amibient temps and never had a problem. Second: You haven't ruled out.....and have only assumed...other issues. Some of those symtoms are caused by the mixture being to rich...and not lack of fuel. From your description...when it's hot. IE...the MPS diaphram is made from a Berrilium copper so if it is even slightly cracked...would leak more when warm. Ask me how I know this. Third...looks like some one did some re-wiring for the fuel pump. The leads IIRC for that pump run through the FI harness and looks to have been bypassed. The source comes from the FI board and fuses. Electrical connections if dirty or loose connections expand when they are hot.....so has that been ruled out? Is your board clean and fuses clean...cause if they are dirty...the resisitance caused by heat will cause them to expand even more. The worst circuit design on the 914 in my opinion was the fuel circuit becuase it is switched through the ignition and then relayed through the primitive trace board and fused as a safety feature. You need to make sure this is ALL working and clean before you start chaseing your tail. I don't think relocating your fuel pump will solve that problem if it does then you just eliminated bypassing something you didn't check or mis-diagnosed. Good luck. |
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