1970 911 2.2 stalls when warm.

[Alex4911]

Hey Folks ! Wonder if someone could help me here. I have a newly acquired 1970 911t with 2.2 engine. It's starts fine runs well until around 180 ish degrees then it's starts stalling and backfiring until it stops. It' won't restart until it cools down then does the same thing once temp rises again. So far all I did was replace the plugs (they were old) but no change. Anybody experience this before. Thanks Alex

[mysocal911]

First, check for a spark. If OK, then use a small about of starting fluid into the air cleaner.

Read here under No-Start; https://www.systemsc.com/diagnostic.htm

[Alex4911]

Hey thanks ! So u suggest to start engine get it warm to the point of where it starts to fail then check spark at that point? If I have good spark then spray some starting fluid to see of that helps it start ? My worry is it won't stay running when it's warm each time it gets up to temp ot fails then only restarts when it's cold. I will check the spark though but spraying starter may not help what are your thoughts thanks

[Alex4911]

Thanks for the reply. I'm going to verify spark when engine gets to the 180 range and fails. If spark is bad I will chase that but if spark is good the engine won't run till it cools down I'm thinking the starter fluid won't help it may start but I don't think it will run as when the engine reaches the 180 it starts to run real rough. Any thougha

[ed mayo]

Problem from temperature or running time could be igntion coil over heating or intank filter clogged. Are you losing spark or fuel?

[Alex4911]

I'm going test fuel pressure and spark. Gotta get some gauges etc. Thanks for the info 👍

[tobluforu]

My 72 did this a long time ago. Chased my tail for weeks. Turned out to be the fuel line from the tank was so old it was collapsing. Ran great for about 10 or 15 minutes. Check fuel lines too.

[Alex4911]

Finally got a fuel gauge installed. Fuel pressure is steady at 3 psi. Spark was yellow at cold (good start ) and yellow at warm (bad start). Should spark be bright blue ? And is 3 psi ok for fuel pressure any thoughts. At this point since fuel pressure was stable I'm thinking it's gotta be spark side. It's has been upgraded to a MSD but it looks weathered so I'm sure it was used

Let me know what u guys think thanks again for your help .

[ed mayo]

Fuel pressure is fine, I think you need to try a new coil.

[Alex4911]

I tired a new coil and same issue. Fuel pressure seems to be lower now. I'm reading between 2 and 2.5 now.

[RSBob]

Tired plug wires can cause the same. Happened to me. Starts fine, warms up, sputters and dies. Wait until engine cools and would start fine. Unless you wires are relatively new, change them - good insurance anyway.

[Alex4911]

Ok makes sense thanks for your help

[Alex4911]

Changed the wires and same thing is happening. It definitely runs smoother while cold with the new coil and wires but still stalls out it gets warm. I did see fuel drop to under 2 psi last night. Think I'm going to pull fuel screen in tank and change out fuel filter next. Fuel system as been modified so there's a small inline filter under car next to tank vs the large canister style in engine bay. Any thought guys ?

[ed mayo]

Yes, absolutely. clean tank filter and change the add on filter.

[Alex4911]

Check out the screen ... not much to clean on this it's completely gone. I hope the small inline filter picked up any of the junk.

[rowingone]

I would remove the fuel sending unit from your tank and look inside. You might have corrosion that warrants a new tank. Or remove small inline filter and replace with one that is clear so you can see any contamination present.

[Alex4911]

Changed the fuel filter and my pressure increased to 3 psi. No improvement though. Still having issues with starting. I re checked spark and it's present , fuel is present to the carbs. Any other thoughts?