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> Car running like crap, 4 days before Hershey
saigon71
post Apr 16 2019, 07:29 PM
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Could use some "check this" help:

Running a 2056 D-jet.

Over the winter I adjusted the valves and changed the oil. It didn't need much else.

This Spring, I installed a new distributor cap and new set of points. Adjusted dwell to 50 degrees before setting timing dead on at 27 degrees BTDC.

The car was running awesome. (IMG:style_emoticons/default/driving.gif)

All of the sudden, the car has developed a pretty serious intermittent miss. There have been times it runs flawless on a test drive, only to start sputtering the next drive. When the sputtering and bucking occurs, there is sometimes an audible "pop" or "knock" sound coming from the engine bay.

I've got a new FI wiring harness from Jeff Bowlsby installed.

So far I have done the following:

-Check fuel lines for kinks
-Added "Star-Tron" enzyme fuel treatment to fuel stored in tank for winter, have since added two tanks of fresh gas
-Fuel steady pressure at 31PSI (but I couldn't get the car to act up when I had the gauge attached)
-Verified point gap hadn't changed after setting dwell
-Verify that CHT is tight (CHT is almost new)
-Cleaned & adjusted trigger points
-Unplugged TPS - it did not make a difference
-Checked FI harness grounds at the back of the engine
-Pulled all 4 spark plugs to check for fouling - they all looked good
-Swapped the coil with a known good one

Any advice on other things to check would be appreciated.
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Minerva's 914
post Apr 16 2019, 07:36 PM
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I would check the points, it's a cheap and easy check and apparently the likelihood of a defective set of points is greater than one might imagine according to a long time friend that has been a 914 starwort for 40 years.
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Big Len
post Apr 16 2019, 08:01 PM
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QUOTE(Minerva's 914 @ Apr 16 2019, 09:36 PM) *

I would check the points, it's a cheap and easy check and apparently the likelihood of a defective set of points is greater than one might imagine according to a long time friend that has been a 914 starwort for 40 years.

(IMG:style_emoticons/default/agree.gif)
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wndsrfr
post Apr 17 2019, 06:07 AM
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QUOTE(Minerva's 914 @ Apr 16 2019, 05:36 PM) *

I would check the points, it's a cheap and easy check and apparently the likelihood of a defective set of points is greater than one might imagine according to a long time friend that has been a 914 starwort for 40 years.

Put the old dizzy cap back on
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VaccaRabite
post Apr 17 2019, 06:30 AM
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When the car is acting up, put a timing light on the different plug wires and see which one is acting funny.

I agree with the others that your issue sounds electrical. Could be a faulty plug wire.

Zach
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rgalla9146
post Apr 17 2019, 07:29 AM
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Not mentioned: plenum and intake manifolds for vacuum leaks or cracked hoses.
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dr914@autoatlanta.com
post Apr 17 2019, 07:44 AM
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can you get it to do it when the car is stationary, or do you have to drive it and put a load on the engine?
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saigon71
post Apr 17 2019, 10:39 AM
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QUOTE(dr914@autoatlanta.com @ Apr 17 2019, 09:44 AM) *

can you get it to do it when the car is stationary, or do you have to drive it and put a load on the engine?


I notice it most under load, but noticed it happening stationary as well when I rev the engine.
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Spoke
post Apr 17 2019, 10:56 AM
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Does the tach bounce or jump when this happens? Sometimes that could signal ineffective burn or ignition issues.
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dr914@autoatlanta.com
post Apr 17 2019, 10:56 AM
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so rev the engine and pull one spark plug wire at a time from the cap and try to localize it to a cylinder or two. If two diagonal cylinders, trigger points, if two on the same Side injector grounds if only one then switch the injector leads and see if it moves and switch the plug wire with another one

QUOTE(saigon71 @ Apr 17 2019, 09:39 AM) *

QUOTE(dr914@autoatlanta.com @ Apr 17 2019, 09:44 AM) *

can you get it to do it when the car is stationary, or do you have to drive it and put a load on the engine?


I notice it most under load, but noticed it happening stationary as well when I rev the engine.
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saigon71
post Apr 17 2019, 06:36 PM
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Update:

The trigger to the poor running is turning the headlights on. Almost immediately, the car starts jerking and I hear the knock sound.

Battery is new. Resting voltage is 13.06, it is 13.6 running without lights and drops to 12.5 running with the lights on. Alternator belt seems fine.

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Spoke
post Apr 17 2019, 07:17 PM
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Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil?

With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR.
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saigon71
post Apr 17 2019, 07:36 PM
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QUOTE(Spoke @ Apr 17 2019, 09:17 PM) *

Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil?

With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR.


13.6 running without lights on, 12.5 running with the lights on. Both measurements taken at the battery, car idling at 1100 rpm or so.

I'll run your other tests tomorrow after work.
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Spoke
post Apr 17 2019, 07:37 PM
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QUOTE(saigon71 @ Apr 17 2019, 09:36 PM) *

QUOTE(Spoke @ Apr 17 2019, 09:17 PM) *

Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil?

With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR.


13.6 running without lights on, 12.5 running with the lights on. Both measurements taken at the battery, car idling at 1100 rpm or so.

I'll run your other tests tomorrow after work.


Does the battery voltage come up w/lights on as RPMs rise?
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Olympic 914
post Apr 18 2019, 07:46 AM
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13.6 seems low.

Had a recent issue where it was charging at that and after a 30mi. drive the battery was too low to start the car. first I suspected the new radio amp I had installed was drawing too much. but then found that the alternator belt was loose. it was probably slipping more at higher rpms, replaced the belt ($10 insurance) tightened it up and its now charging at 14.1, no other changes.

I did read where you stated the belt on yours seemed okay.

will still be bringing my jump start box to Hershey.

and AAA card.

Hope you get it sorted.
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dr914@autoatlanta.com
post Apr 18 2019, 09:43 AM
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13.6 is great, sounds like a grounding problem, check the battery neg to right firewall connection, the ground leads at the back of the engine case on top and the rear trans mission to bottom of the trunk floor

QUOTE(Olympic 914 @ Apr 18 2019, 06:46 AM) *

13.6 seems low.

Had a recent issue where it was charging at that and after a 30mi. drive the battery was too low to start the car. first I suspected the new radio amp I had installed was drawing too much. but then found that the alternator belt was loose. it was probably slipping more at higher rpms, replaced the belt ($10 insurance) tightened it up and its now charging at 14.1, no other changes.

I did read where you stated the belt on yours seemed okay.

will still be bringing my jump start box to Hershey.

and AAA card.

Hope you get it sorted.

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ctc911ctc
post Apr 18 2019, 01:22 PM
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[quote name='dr914@autoatlanta.com' date='Apr 18 2019, 09:43 AM' post='2706434']
13.6 is great, sounds like a grounding problem, check the battery neg to right firewall connection, the ground leads at the back of the engine case on top and the rear trans mission to bottom of the trunk floor

[quote name='Olympic 914' post='2706413' date='Apr 18 2019, 06:46 AM']
(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)

Or, number 329 in the 700 TT book should be considered!

13.6 is the right potential for optimally charging Lead/Acid Batteries to maximize the life of the cells.
https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery
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saigon71
post May 5 2019, 11:27 AM
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QUOTE(Spoke @ Apr 17 2019, 09:17 PM) *

Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil?

With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR.


Damn this is frustrating. (IMG:style_emoticons/default/headbang.gif)

I discovered I had an adjustable voltage regulator and bumped up the voltage slightly.

Still battling this problem. I installed a reman "Carquest" alternator from NAPA. Things got better, but the car still bucks when I drive it with the lights on.

Spoke: I measured the voltages as you suggested with the new alternator at 2000 RPM. These are my readings:

D+: 14.5V
DF: 3.2V
D-: negative 62 millivolts

Does the low reading at DF indicate I got a bad rebuilt alternator?
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saigon71
post May 5 2019, 11:30 AM
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QUOTE(Spoke @ Apr 17 2019, 09:37 PM) *

QUOTE(saigon71 @ Apr 17 2019, 09:36 PM) *

QUOTE(Spoke @ Apr 17 2019, 09:17 PM) *

Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil?

With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR.


13.6 running without lights on, 12.5 running with the lights on. Both measurements taken at the battery, car idling at 1100 rpm or so.

I'll run your other tests tomorrow after work.


Does the battery voltage come up w/lights on as RPMs rise?


Battery voltage increases slightly with lights on as RPM's rise from 13.6V to 13.77V
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ejm
post May 5 2019, 12:05 PM
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You need to check the voltage at coil terminal #15 and maybe at pin 1 of the white 4 pin FI harness plug on the relay board. High resistance somewhere will reduce voltage to the consumers. I would plug another ignition switch into the harness and see if the problem goes away.
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