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> Car never ran better - THEN!, Seems when hot there is no low end power
ctc911ctc
post Jun 25 2023, 04:30 PM
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'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
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emerygt350
post Jun 25 2023, 05:55 PM
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Do you still have the original distributor?
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r_towle
post Jun 25 2023, 06:09 PM
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Advance plates sticking in distributor
Fuel pump needs replacing
Head temp sensor is toast
Check all grounds
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r_towle
post Jun 25 2023, 06:13 PM
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What location did you put the fuel pump?
If it’s in the engine bay, make sure the heat exchanger is not blowing air on the fuel pump
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burton73
post Jun 25 2023, 06:23 PM
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http://www.914world.com/bbs2/index.php?showtopic=295025

read up on vapor locking.

search with google and as any question and 914world and it will bring up examples

That works for me

Bob B
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SirAndy
post Jun 25 2023, 06:24 PM
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QUOTE(ctc911ctc @ Jun 25 2023, 03:30 PM) *
Car never ran better

Back in my dirt bike racing days, that was a sure sign that something was about to go kaputt.

They always seemed to run "better than ever" right before failing in a spectacular way.
(IMG:style_emoticons/default/popcorn[1].gif)
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ctc911ctc
post Jun 25 2023, 06:27 PM
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Ain't it the way!
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ctc911ctc
post Jun 25 2023, 06:30 PM
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Vapor Lock did not occur to me - the pump is in the same place as stock - I move it a bit to make it "out of the way", will take a look at it.....

Would Vapor lock at the fuel pump result in a reduction in pressure at the rail? If so would this persist once the engine was running at higher RPMs?



QUOTE(r_towle @ Jun 25 2023, 06:13 PM) *

What location did you put the fuel pump?
If it’s in the engine bay, make sure the heat exchanger is not blowing air on the fuel pump
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ctc911ctc
post Jun 25 2023, 06:33 PM
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I took the plates out, cleaned and rebuilt the entire assembly - tried to find a new one, however, could not find one for a stock Injector setup......

Will look within the board, Would be nice to have a spare - also, do you think it would be heat sensitive?

The advance plates once I was finished were pretty slick, the springs very taught and new


QUOTE(r_towle @ Jun 25 2023, 06:09 PM) *

Advance plates sticking in distributor
Fuel pump needs replacing
Head temp sensor is toast
Check all grounds
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ctc911ctc
post Jun 25 2023, 06:35 PM
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Yes,

I took it apart and cleaned it.....twice! Seems like it is all together correctly and very clean - spring plates are free and move nicely .......would this behavior be temperature sensitive?



QUOTE(emerygt350 @ Jun 25 2023, 05:55 PM) *

Do you still have the original distributor?
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r_towle
post Jun 25 2023, 07:14 PM
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Well, fuel and ignition
Can you reproduce the problem , near home?

I’m thinking hot coil, or hot fuel pump
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ctc911ctc
post Jun 25 2023, 07:25 PM
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Yes, I know how to reproduce - will adjust/check, adjust/check tomorrow or later this week!



QUOTE(r_towle @ Jun 25 2023, 07:14 PM) *

Well, fuel and ignition
Can you reproduce the problem , near home?

I’m thinking hot coil, or hot fuel pump
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r_towle
post Jun 25 2023, 09:04 PM
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If you need anything, give me a ring.

Rich
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rjames
post Jun 25 2023, 10:41 PM
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Unlikely it’s your issue, but one summer my car would run great and then stall intermittently after it warmed up. Sometimes I could drive for hours before it would happen, sometimes 30 minutes or less. I’d have to keep the RPMs up to keep it from stalling. Sometimes it would stall anyway.
Turned out the computer was bad. Likely a failing solder joint that would worsen with heat.
Intermittent issues are the worst.
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emerygt350
post Jun 26 2023, 03:43 AM
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Can't say enough about the 123dizzy. However it sounds like you have yours in good shape.

The fact it is low rpm really makes me lean that way. You say runs fine over 1500 but does it really? I have had bad coils on other cars behave like that, at higher rpm it was harder to notice, normally that results in bucking at low rpm cruise though.

I really don't think this is a vapor lock.
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Cairo94507
post Jun 26 2023, 06:30 AM
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On a hill and stopped for a long time... how much gas was in the tank? (IMG:style_emoticons/default/beerchug.gif)
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76-914
post Jun 26 2023, 07:52 AM
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QUOTE(ctc911ctc @ Jun 25 2023, 05:30 PM) *

Vapor Lock did not occur to me - the pump is in the same place as stock - I move it a bit to make it "out of the way", will take a look at it.....

Would Vapor lock at the fuel pump result in a reduction in pressure at the rail? If so would this persist once the engine was running at higher RPMs?



QUOTE(r_towle @ Jun 25 2023, 06:13 PM) *

What location did you put the fuel pump?
If it’s in the engine bay, make sure the heat exchanger is not blowing air on the fuel pump


Absolutely. It's very difficult to pressurize a vapor as compared to a liquid. The vapor lock occurs in the pump or in the incoming line. I vaporized upon takeoff and almost shit in my pants. I had been on the tarmac for awhile and it was a hot day.Twenty feet off the runway it began sputtering so I had to slam the plane back down on the runway and full brakes before I ran out of runway! I was running auto gas and it vaporizes quite easily compared to AvGas. (IMG:style_emoticons/default/beerchug.gif)
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ctc911ctc
post Jun 26 2023, 09:18 AM
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Yes, my mind did go there - the tank was completely rebuilt with new sending unit, sock, filter and at the time of the stalling was reading over 1/2 tank.


QUOTE(Cairo94507 @ Jun 26 2023, 06:30 AM) *

On a hill and stopped for a long time... how much gas was in the tank? (IMG:style_emoticons/default/beerchug.gif)
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emerygt350
post Jun 26 2023, 03:21 PM
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That gets worse with load/rpm. This apparently works fine with load/rpm.
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ctc911ctc
post Jun 27 2023, 01:13 PM
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Conscious that makes Sens-ous is that the fuel pump is getting too hot and the machine is getting the vapors.......will move the fuel pump or re-route this weekend and report
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