Hard to start after ~7 day sit

[mike sampsel]

I need to crank for ten to twenty seconds and apply pedal to get the engine to come to life.

If I start it in two to three days since the last start, it fires in 2 - 3 sec.
If I start it up when warm it fires immediately.

I've checked fuel pressure (FP) with a gauge, and it's in spec, however:

A.) Have not checked FP when the cranking problem arises.
B.) The Fuel Pump pressure was on the low side of the spec

Here is what I obtained with the engine not running a while back

System Pressure between 4.6 and 4.7 (Bars Needle shakes between values)
Cold WUR (power off) 2.2 (Needle steady)


I've seen comments in posts on this issue: check for un-metered air. The engine dies when I turn the idle knob all the way in so I doubt it is a vacuum leak issue. If it were, why would it occur after sitting a week, why not hard to start after 3 days?

My TTS is suspect, looks "live" too long (read 12v at the ground side after 1 minute of 12 volts applied to the yellow wire side), so after cranking for 3 sec, I disconnected the ground to the (red/bk wire on the TTS) CSV side, and still took a long time to start.

Seems the easy start after sitting for three or so days, might eliminate the CSV from the list of culpability to the long-sit cold start?

Looking for suggestions on what steps to take to determine the source of the issue.

Run a pressure test while long cranking occurs? Try a start after sitting but prime the injectors first as a test? Others?

Issue is not a show stopper, just an annoyance for a cold start video when if I sell in five years.

[al lkosmal]

The Fuel accumulator will keep the fuel pressure up for short periods, but the check valve, located on the fuel pump, is designed to keep the fuel in the lines from running back into the tank. If it fails......it will then take longer to start your engine, as the pump needs to refill the lines.

regards,
al

[boyt911sc]

Mike,

Next time you have the car sit for a week or more, do this test. Before you start the car, test run the FP for a few seconds and start the motor. Do not assist or touch the gas pedal. Have the car in NEUTRAL and reach for the ignition switch through the window. Don’t get in the car. Did the car start the first time? How many times before it started? Keep us posted. Thanks.

Tony

[mike sampsel]

Originally Posted by boyt911sc

Mike,

Next time you have the car sit for a week or more, do this test. Before you start the car, test run the FP for a few seconds and start the motor. Do not assist or touch the gas pedal. Have the car in NEUTRAL and reach for the ignition switch through the window. Don’t get in the car. Did the car start the first time? How many times before it started? Keep as posted. Thanks.

Tony

I’ll do it, test run via the appropriate wires across the FP relay for 5 sec, is what I’ll do.
Thanks for the ideas.

[Gretz]

I'll add that one thing that hindered my CIS problem solving is that a previous owner disconnected the connection on the forward side of the engine that stopped the fuel pump from running when the engine is off but the ignition is on. That meant that my fuel pump started running even before trying to start the car. You probably don't have this issue, but I did and I'm pretty sure it's rare.

[boyt911sc]

Originally Posted by mike sampsel

I’ll do it, test run via the appropriate wires across the FP relay for 5 sec, is what I’ll do.
Thanks for the ideas.

There are several ways to test run the fuel pump of a CIS without running the motor. With the ignition switch @ ON:

• Remove the FP relay and jumper terminals 87a & 30 at the relay socket.
• Unplug the air flow sensor switch connector.

Tony

[mike sampsel]

Originally Posted by boyt911sc

Mike,

Next time you have the car sit for a week or more, do this test. Before you start the car, test run the FP for a few seconds and start the motor. Do not assist or touch the gas pedal. Have the car in NEUTRAL and reach for the ignition switch through the window. Don’t get in the car. Did the car start the first time? How many times before it started? Keep us posted. Thanks.

Tony

Tony,

Today I jumped the FP for about ten sec. From outside the car, I turned key for 2 sec, it tried to start. Let go tried again for 2 sec, it tried to start. Third try it started in about 2 sec and got to ~ 1300 rpm in about 2 sec. So a big improvement over the (not running the pump) cold start. Turned off, started right up ten minutes later.

May be time for a new fuel pump?

[boyt911sc]

Originally Posted by mike sampsel

Tony,

Today I jumped the FP for about ten sec. From outside the car, I turned key for 2 sec, it tried to start. Let go tried again for 2 sec, it tried to start. Third try it started in about 2 sec and got to ~ 1300 rpm in about 2 sec. So a big improvement over the (not running the pump) cold start. Turned off, started right up ten minutes later.

May be time for a new fuel pump?

Test and verify that the FP is defective before replacing it. If you are getting 70 psi. system pressure, then you don’t need a new fuel pump. What is your system pressure?

Tony

[mike sampsel]

Originally Posted by boyt911sc

Test and verify that the FP is defective before replacing it. If you are getting 70 psi. system pressure, then you don’t need a new fuel pump. What is your system pressure?

Tony

System pressure (one year ago) was a shaky needle between 4.6 and 4.7 bars. or 67-68 PSI. So not quite 70 psi.

[mike sampsel]

So if an SC sits for weeks and all is correct, it should start up right off?

What does the apparent improvement in starting mean after I run the fuel pump for some time?

Is there another test or diagnosis to run?
Maybe run the FP test after the car has sat for sometime?

[Joe Bob]

The check valve that Al mentioned is a frequent culprit and cheap. My CV issue was hot start related. A spritz of ether always fixed it but that was a PITA.

[al lkosmal]

Originally Posted by mike sampsel

So if an SC sits for weeks and all is correct, it should start up right off?

What does the apparent improvement in starting mean after I run the fuel pump for some time?

Is there another test or diagnosis to run?
Maybe run the FP test after the car has sat for sometime?

Mike........The Fuel accumulator will keep the fuel pressure up for short periods, but the check valve, located on the fuel pump, is designed to keep the fuel in the lines from running back into the tank. If it fails......it will then take longer to start your engine, as the pump needs to refill the lines.

regards,
al

[mike sampsel]

Originally Posted by Joe Bob

The check valve that Al mentioned is a frequent culprit and cheap. My CV issue was hot start related. A spritz of ether always fixed it but that was a PITA.

Cheap caught my attention.

Thanks

[mike sampsel]

Originally Posted by Joe Bob

The check valve that Al mentioned is a frequent culprit and cheap. My CV issue was hot start related. A spritz of ether always fixed it but that was a PITA.

Originally Posted by al lkosmal

Mike........The Fuel accumulator will keep the fuel pressure up for short periods, but the check valve, located on the fuel pump, is designed to keep the fuel in the lines from running back into the tank. If it fails......it will then take longer to start your engine, as the pump needs to refill the lines.

regards,
al

Well there it is again, sometimes it takes me a few trys to get it.

Thanks,

al ikosmal

[boyt911sc]

Mike,

Have you tested and confirmed that the CSV is spraying fuel during a cold start? Another thing you need to confirm is the spray patterns of the fuel injectors. This is one of the most neglected tests. You need an atomized mist-like v-shape spray pattern from the injectors.

Aside from a good residual pressure, spray pattern is desirable for easy start up.

Tony

[mike sampsel]

Originally Posted by boyt911sc

Mike,

Have you tested and confirmed that the CSV is spraying fuel during a cold start? Another thing you need to confirm is the spray patterns of the fuel injectors. This is one of the most neglected tests. You need an atomized mist-like v-shape spray pattern from the injectors.

Aside from a good residual pressure, spray pattern is desirable for easy start up.

Tony

Hi Tony, always a pleasure to get your thoughts,

My injectors are new (about 3 K miles on them), I suspect they are fine, but I have not tested them.

If the CSV, were the cause, why would a cold start after 2 days of rest work without a hitch? Seems the cold start in two days rest, would need the CSV to function just as much as one with a weeks rest? I need to try a cold start tomorrow morning to verify it is hitch free.

[Flat6pac]

Mike, on a 77-79 the check valve is part of the fuel pump so the whole unit gets replaced.
Bruce

[boyt911sc]

Mike,

What is the result of the test about running the FP before starting? Any significant result you like to share with us? Another test you could try is disconnecting the AFS plug. Turn the ignition switch @ ON (not start) for several seconds and START the car. Let us know if you observed any difference at all with the AFS plug removed. Keep us posted.

Tony

[mike sampsel]

Originally Posted by boyt911sc

Mike,

What is the result of the test about running the FP before starting? Any significant result you like to share with us? Another test you could try is disconnecting the AFS plug. Turn the ignition switch @ ON (not start) for several seconds and START the car. Let us know if you observed any difference at all with the AFS plug removed. Keep us posted.

Tony

Hi Tony,

So I ran the pump (jumped from 30 to 87a on relay pins) for about 10 sec.

From outside the car I turned the key.

First try with ~3 sec, car tried to start let key go but not start.
Second try again ~ 3 sec of key, car tried to start let key go but not
Third try with 3 sec of key the car started and after a couple of sec idle at ~ 1300 rpm.

Seems better than the 15 to 20 sec of constant key without jumping the pump.

And today after sitting for 2 days, car starts up after 3 sec of key.

[mike sampsel]

Originally Posted by boyt911sc

Mike,

What is the result of the test about running the FP before starting? Any significant result you like to share with us? Another test you could try is disconnecting the AFS plug. Turn the ignition switch @ ON (not start) for several seconds and START the car. Let us know if you observed any difference at all with the AFS plug removed. Keep us posted.

Tony

Well with cooler weather in the morning, I started the car after sitting for 10 days. Fired right up with no hesitation! Roared to 2000 rpm and settled down quickly to 1200 then 1100 rpm (JW told me to set my WEB cam 20/21 idle there). So this does not seem to be a check valve issue. I will let it sit longer sometime and try again with this "colder" weather.

Anyway, I've not tested the CSV yet, this response makes me question the TTS. When I tested the TTS (a ways back) by placing 12 volts to the plus side (yellow wire side) for over a minute, I measured 100 ohms on the other side to ground (50 ohms across, was 24 ohms across before applying the 12 volt source). Seemed not very an "open" TTS to me. Was back to zero ohms to ground very quick? So suspecting my TTS might be faulty and allowing a flooding of the car when it sits? No flood when sits for a few days?

I'm going to let it sit for 2 weeks and try again to see if it fires right up. One thing I've learned is to keep the key on continuously during the starting process. No on and off trying ... maybe it was operator error before?

Cheers