M20 B25 Hard starting when warm/Hot

[Andy325i]

What could this be?

It eventually goes after a lot of cranking.

Starts fine when cold

Thinking blue temp sender?

Many thanx

Andy

[pnd]

this is a tricky one i have had this problem on several 325's and never solved it despite changing both temp senders.

[Brianmoooore]

If it was temp. sensor related, it would most likely run poorly when hot, as well as be difficult to start.
More likely to be ignition component related, giving a reduced spark with the low battery voltage while cranking, or be a leaking injector or two.
Does it start easily if the attempt to restart is almost immediately after it has stopped, or does the problem only arise if left for several minutes?

[Andy325i]

Hi Brian, not sure but will give it a try

Distributor cap, rotor arm and plugs aren't that old. Well that said, probably about 18 months now but done less than 2000 miles


Andy

[Andy325i]

Right had a chance to look at it today, hardly started when cold, had a look and the Fanbelt and P/S belt are hanging off. Will get new ones ordered and a new set of plugs for good measure

Andy

[tha881]

This used to happen on my car, always fired up first time from cold but sometimes when warm you had to keep cranking it. I found that pumping the pedal a bit as you turn the key would help.
Anyway i changed intake manifolds a few weeks ago and it seems to have cured it. The car has done about 135k but the intake runners had a lot of carbon build up. I can only asume when hot this was running down into the cylinders and fouling the plugs? It has been pretty much perfect since i put the clean one on.

[soul4t]

Hi Brian, not sure but will give it a try

Andy

Did you try starting it just after shut off?...Could be residual fuel pressure, I had a similar problem and retrofitted a check valve on the fuel supply line, under the fuel pump cover. Cured mine!

[Andy325i]

It's like it if you start it 30 secs after it's been switched off or 15 mins. Slightly annoying lol!

[jonny323i]

I'm sure some had a similar problem and it was poor ht leads

[foggy50361]

I've always thought this was down to the fuel rail absorbing the heat of the engine when shut off causing low pressure, until when cranking the rail pressure is restored then whooa there she goes.

foggy

mine goes first turn when cold, 5-10s or so when warn/hot