Cold Start Issues

[Rotary Potato]

Afternoon all.

Following my rebuild, the car has been starting beautifully, as you'd expect. Did a track day on 29th Jan, it was faultless. Parked it up on 29th after unloading and all seemed good.

Went to fire it up today and it took 3-4 bursts of 6-7 seconds on the starter to get it to fire. Drove 40 miles to the Midlands meet, and it drove great. Parked up and had lunch. Went to start it a few hours later (about 2 1/2 hrs later) and same deal. Eventually fired up on about the 3rd or 4th burst on the starter - which was definitely spinning slower than usual by this point.

Again, 40 mile drive home was great. Stopped for fuel, and it fired right up on the first turn of the key.

Any ideas?

My thought after the first one was that battery was slightly drained after unloading the car (doors and boot open for 10-20 mins) and then pumping tyres back up to road pressure from track pressures with a battery powered compressor. But surely a spirited 40 mile drive would top it back up, so doesn't explain the second cold start.

[qwakers]

knackered battery and/or starter? bad earth?

the only things i can think of.

[PeteH]

It's bound to be your battery. 40 miles won't get close to recharging it.

I lay mine up for a month between events, and four months over the winter. I would never consider trying to start it without giving it a few hours on the charger first. And I don't have much left on the car to drain the battery....

[Rotary Potato]

I have a multimeter ... but I'm an electrical doofus.

Is it as simple as switching to to volts and tapping the probes to the terminals?

Battery is a 12 month old Varta.

[Dazza44]

Yep that will give u the output

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[PeteH]

It doesn't mean your battery is dead. It just means that if you ask too much of it during winter it will struggle. Give it a hand by giving it a good charge if you leave the car for a while, or suck charge from it with compressors and so on.

Yes, just turn your multi-meter to DC volts, ensure the range can read up to at least 20v, then put one probe on each terminal of your battery. You should see about 12.7v on a good battery that has been left idle for an hour or two. If it is reading 12.5v or less then get a charger on it before trying to start your car.

[Rotary Potato]

12.88 volts about 90 mins after last driving it.

[Rotary Potato]

A quick google says that batteries retain charge for a period after car was last used, so will measure again tomorrow after work.

https://haynes.com/en-gb/tips-tutorials ... ar-battery

[Rotary Potato]

12.66 volts just now - not run the car since about 5pm last night, so does that mean the battery is good?

Assuming so, any thoughts on where to look next?

[350matt]

thats reasonable

thing is voltage in its own doesn't really tell you battery capacity
best test is a load test
see here

if you have a scan tool then plug that in when cranking to monitor the engine speed as it needs to be at least 180rpm - ideally more

[Rotary Potato]

Thanks Matt.

At the compression test about 6 months ago it was cranking (hot) at almost 270rpm. I'll check where we are now at next start up.

[Rotary Potato]

An update.

After 6 days of being sat, the battery was holding 12.55 volts. My multimeter doesn't have a min/max function, so can't do the test Matt posted above.

However, it held between 265rpm and 220rpm over a 10 second crank without starting. I floored the accelerator on the second cranking and it fired up in about 2 seconds.

When running the battery shows between 14.35-14.40 volts.

I let it warm up on driveway for about 10 mins, switched off and attempted a restart. It fired up immediately.

Any thoughts. It just seems really unhappy cold starting!

[warpc0il]

Does the engine idle cleanly when cold?

It could be that the Intake Air Temperature sensor is faulty and the PCM isn't selecting the right map for a cold start.

When did you last reset the PCM and was the engine stone cold when you did?
viewtopic.php?f=25&t=34703

[Rotary Potato]

Hi Dave,

Difficult to say as I'm still getting used to the rebuild with the full bridgeport.

I haven't done a reset, but assume Rotary Revs would have done as part of the rebuild (Dec '17) & subsequent mapping session (Jan '18).

I've only done about 5 cold starts since being mapped, and the last 3 have definitely been difficult.

[boosted]

Poss failing fuel pump blocked filter...try ign 2 position 10 times b4 attempting a cold start...there is fuel system prime on start...
Just thinking could be taking all that cranking to repressurise fuel system.

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[Rotary Potato]

Current IAT is 34 degrees (at 1.77 volts), but engine is still warm from running earlier. Will leave it a couple of hours and take the reading again.

Boosted - do you mean ig2-off-ig2-off- ... cycled for 10 times before firing up? If so, do i hold ig2 for any length of time, or just flick it back and forth?

[boosted]

Yes mate on off ign 2 position...fuel pump gets a quick on off prime b4 starting ...worth a try...try at least 10 times...so about 10 seconds of fuel pump priming before firing.


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[warpc0il]

Current IAT is 34 degrees (at 1.77 volts), but engine is still warm from running earlier. Will leave it a couple of hours and take the reading again.

You need to see what the IAT reads when the engine is really cold - should be about the same as the AAT - as shown on the dash display when you press the AMB button.

[Rotary Potato]

Current IAT is 34 degrees (at 1.77 volts), but engine is still warm from running earlier. Will leave it a couple of hours and take the reading again.

You need to see what the IAT reads when the engine is really cold - should be about the same as the AAT - as shown on the dash display when you press the AMB button.

Exactly what I was going to do about 8:30 tonight.

[Rotary Potato]

IAT reading 14 degrees. Ambient showing 8 degrees.

[warpc0il]

Try again in the morning, as there might still be some residual warmth.

[Rotary Potato]

No worries - will do. At that temp I tried to start it.

I tried cycling to ig2 and back 10 times. It spun enthusiastically for a second (like it wanted to start) without firing before slowing slightly. After a further second I floored the throttle pedal and it roared straight into life.

After today it definitely feels fueling related to my simple mind ...

After a 20 mile "blow away the cobwebs" drive, it definitely has more than a little residual heat in it now!

[warpc0il]

You should never touch the throttle pedal when starting the engine.

If you do then the starting fuel maps get screwed up and the engine then won't start from cold.

You need to do a PCM reset in the morning.

Flooring the pedal is used to tell the PCM to engage de-flood mode.

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[Rotary Potato]

Last 2 starts have been achieved with the throttle floored.

Potentially a stupid question. The car has a full bridgeport and been remapped by Rotary Revs to suit. Will I screw anything up by doing a PCM reset on a mapped engine?

[Rotary Potato]

I'm a long way from any sort of expert ... but it feels to me like the car is overfuelling on initial start up, hence why it won't fire up. Then when I floor the throttle pedal it cuts the fueling, correcting the overfueling and the car fires up.