Improve cold start time?

[chaseincats]

Is it possible to improve cold start cranking time?  The car has new plugs, wires, cap, rotor etc and runs great once its started.  It's also worth noting that after the car has started once, it will start considerably quicker the next key turn (demonstrated on the video).

Video: https://www.youtube.com/watch?v=yiT8P_TLuLM

My old mechanic said it simply does this because the engine "just takes longer to build pressure than other cars."  There are no vacuum leaks (checked with a cigar) but there is oil blowby via either worn piston rings or valve seals (I know that due to there being a small amount of oil on the plugs) but I'm not sure if that could be the reason.

Note: this video was created when it was about 80 degrees out so the cold start injector was not firing.

 

Any ideas?

 

-chase

[Captain Obvious]

Mine does that too. I suspect your fuel check valve on the output side of your fuel pump doesn't hold pressure overnight. It holds for some shorter period of time (seconds, minutes, hours?) but not enough hours for it to have fuel pressure for that first cold start of the day.

To test that theory, you can force your fuel pump to run and build pressure before you try to start the key. Couple different ways to accomplish that depending on the year, but the one failsafe version is to disconnect the small spade connector to the starter solenoid and then turn the key to "START". You should hear the fuel pump run. And I bet you'll be able to hear the difference when the pressure has reached normal.

After you're convinced the pressure is up to where it should be, reconnect the starter and then start the car.

[chaseincats]

I've tried that and get the same result (I should have mentioned I tried that)

[AK260]

I’ve just written an essay on this in another thread (post 68) that says pretty much what the Captain is telling you above ...

 

 

https://www.classiczcars.com/forums/topic/63901-delphi-mechanical-fuel-pump-stops-pumping-fuel/

 

Other factors are:

 

TIMING: how much base timing do you have on your distributor? After my first and last service / tune up with a UK z specialist, I found that the base timing was set at 0 degrees!!! OK that is an extreme condition but it took quite a lot of cranking to start and proved the point on base timing!! With the 123 ignition distributor I now have 10 degrees base (adding 5 more at 800rpm) and she fires the instant the fuel arrives. In case you aren’t aware, base timing is the timing of the dizzy before any mechanical advance arrives (i.e. timing at idle, typically I have found 15-17 degrees is ideal). When the revs rise, the dizzy adds a total of 12-15 degrees mech advance to that figure, depending on which one you have.

 

COMPRESSION: if you have a worn engine with low compression, it takes a while cranking to build heat in the cylinder. Have you performed a dry and wet compression test? Anything below 160psi is questionable - ideally you want over that figure. If your wet test PSI jumps up then you have worn rings/bores.

 

A NICE HOT SPARK: do you have a decent coil with a decent distributor and decent HT leads? Are your plug gaps set appropriately? The hotter the coil, the more gap you can run so the bigger the spark (FYI, I run 1.2mm with a 1.5ohm flamethrower coil and 8mm HT leads). While HT leads can look OK, you’d be amazed the difference a new set makes to your engine’s responsiveness.

 

Happy hunting!

 

[chaseincats]

6 hours ago, AK260 said:

I’ve just written an essay on this in another thread (post 68) that says pretty much what the Captain is telling you above ...

 

 

https://www.classiczcars.com/forums/topic/63901-delphi-mechanical-fuel-pump-stops-pumping-fuel/

 

Other factors are:

 

TIMING: how much base timing do you have on your distributor? After my first and last service / tune up with a UK z specialist, I found that the base timing was set at 0 degrees!!! OK that is an extreme condition but it took quite a lot of cranking to start and proved the point on base timing!! With the 123 ignition distributor I now have 10 degrees base (adding 5 more at 800rpm) and she fires the instant the fuel arrives. In case you aren’t aware, base timing is the timing of the dizzy before any mechanical advance arrives (i.e. timing at idle, typically I have found 15-17 degrees is ideal). When the revs rise, the dizzy adds a total of 12-15 degrees mech advance to that figure, depending on which one you have.

 

COMPRESSION: if you have a worn engine with low compression, it takes a while cranking to build heat in the cylinder. Have you performed a dry and wet compression test? Anything below 160psi is questionable - ideally you want over that figure. If your wet test PSI jumps up then you have worn rings/bores.

 

A NICE HOT SPARK: do you have a decent coil with a decent distributor and decent HT leads? Are your plug gaps set appropriately? The hotter the coil, the more gap you can run so the bigger the spark (FYI, I run 1.2mm with a 1.5ohm flamethrower coil and 8mm HT leads). While HT leads can look OK, you’d be amazed the difference a new set makes to your engine’s responsiveness.

 

Happy hunting!

 

Thank you so much for these great ideas, I'll tackle them one by one:

Fuel: I tried the pump priming method but that didn't change things.

Timing: I recently changed distributors to a rebuilt one (the old one's center bushing was dying) and with both OEM distributors I get the same result.  The car is also timed at 10 degrees at idle and runs smooth as glass.

Compression: Not sure about the compression (kind of afraid to look haha) but the car runs really well and has great highway pull as-is.

Spark: I changed the plugs last year to the iridium plugs with new ngk leads and all the recommended tune-up brands/gear to no change.  The car also has some sort of ignition box made by "Jacobs electric."  The one spark related issue I can think of is the center terminal on my distributor cap is semi melted - I put some ox-guard on the side of the terminal walls and plug and I believe that helped though.

[chaseincats]

Update: The issue was old/tired/maybe dirty injectors.  Bought new injectors/fuel filter and it starts on the first crank when stone cold.

[chaseincats]

Long term update.

It wasn't the injectors and for the hotter part of the summers that followed, I had the long cold starting issue.  A few months back I added a manual switch in the cabin to bypass the Thermotime switch to get the car to start up on crank 1 or 2 regardless of weather which is awesome and works like a charm.  That said, I replaced my fuel pump a week or so ago due to it being old as heck and pooping out once.  While the car ran great once started, it still had that long cranking issue when it was hot out.

I took the relay bracket out and cleaned the teeth of all of them then used a multimeter set to resistance (ohm) and checked the circuits from the teeth and low-and-behold found resistance.  I pried open the relays that had resistance (fuel pump and main EFI relay - the fuel pump control relay was fine) and found black corrosion on the relay's rocker arms and tabs they connect to once triggered.

After cleaning all of that off, I took another ohm measurement and got basically 0.  I put them back in the car a few days later and without using the what I started calling the 'quick start switch' the car roared to life on crank 3.  I was absolutely floored.

 

All that to say, take your relay bracket out and take some ohm measurements of the circuits in each relay (after cleaning the teeth with a dremel wire brush or something).  If you find anything but "0.02" or below resistance, pry them open and sandpaper off the black corrosion which is no doubt there.

 

Edited September 23, 2022 by chaseincats

[Zed Head]

I see only one start.  Have there been more?  The conductive part of the relay is affected mostly by the contact points. Not really clear what you cleaned up.  Did you take any pictures?

1 hour ago, chaseincats said:

low-and-behold found resistance.

And you reported zero after, but no number before.  How much resistance?  And, to be be picky, the relay would have to be actuated in order to measure the resistance to the components that get the power.  Through the relay circuit.

Just saying, it's hard to tell what you did.  (p.s. it's "lo".)

[chaseincats]

5 hours ago, Zed Head said:

I see only one start.  Have there been more?  The conductive part of the relay is affected mostly by the contact points. Not really clear what you cleaned up.  Did you take any pictures?

And you reported zero after, but no number before.  How much resistance?  And, to be be picky, the relay would have to be actuated in order to measure the resistance to the components that get the power.  Through the relay circuit.

Just saying, it's hard to tell what you did.  (p.s. it's "lo".)

I cleaned 2 things -

1) the "teeth" that sit outside of the relay housing (the things that plug into the harness).  After cleaning the teeth I took resistance measurements between the circuits.  For example (I didn't need to clean this one but it's easy to explain this way) - the fuel pump control relay has 4 teeth.  By activating the relay by touching a 9v battery to the left 2 of the 4 teeth the relay will click, I then measured the resistance of the high power circuit (the side which is actuated by the relay itself)

2) if resistance is found (anything over 0.02ish on the multimeter's ohm setting), I opened up the relay by bending the locking prongs back to pull the top of it off.  Once open you'll see 2 contacts and rocker looking like this:    \ |/    when actuated, the relay arm will shift to    \| /.

For relays that had resistance, there ALWAYS was some sort of black marks either on the contact side \ /    or the relay rocker arm side  |   

Using sandpaper i cleaned them all up and took another measurement confirming there was no more resistance.

Top tip: the screw at the bottom of each relay has nothing to do with opening the casing, it screws the relay electrics to the bottom plastic base.  Unscrew that screw to pull the articulating arms out of the contacts, it makes it WAY easier to clean both sides that way and screws back in easily.

Edited September 23, 2022 by chaseincats

[Zed Head]

I wonder which circuit had the effect.  

[chaseincats]

1 hour ago, Zed Head said:

I wonder which circuit had the effect.  

The main efi relay had some resistance so maybe the efi system wasnt getting full power?  My main guess is the fuel pump relay had resistance, so maybe it took a little bit longer for power to push its way through the corrosion to turn the pump on?  Who knows - all I do know is everyone should test the relays for resistance.  The only reason I resurected this old thread was for that PSA haha

[Patcon]

My theory would be increased resistance lowers the voltage to the pump. Lower voltage turns the pump slower and with less force. Increasing cranking time waiting on fuel