hot starting problems

[boofs]

I have a 911E sportsmatic 1969 my problem is not starting when hot I have got it down to a fuel injection problem no fuel being sent to the injectors it seems to be shut off at the bosch mechanical fuel injection pump, there is plenty of fuel/fuel pressure from the fuel pump to the fuel injection pump, this injector pump has the two solenoids fitted an inrichment and a shut off which I have checked and by-passed as not the problem, it seems that if I get the engine up to temperature then stop and start its OK but if I leave it for a half to one hour it will not start no fuel from the injection unit to the injectors but plenty from the fuel pump, on checking the thermostat bolted on the back of the injection pump it seems there could be a shim of 2.11 mm thickness missing between the too although the gasket is present, can any body confirm if this shim should be present on my injection pump and could this cause my problem,any help please, regards,Tony,Totnes,Devon,UK.

 

[early 911]

Could it be this . . . . (not a MFI pro I'm afraid)

Engine is difficult to start when warm, dies at intersections, balks in stop and go operation.
Cause:[FONT=arial mt,arial"]
On some engines (especially 911 E/Model 73), a burr may remain on the end of the thread after the injector holes in the cylinder heads were drilled. This burr will interfere with the injector causing poor injector closing.
This leads to the difficulties mentioned above.

Remedy:​

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1. Remove and check injectors.2. Take a drill of 10.5 mm Ø (fill the grooves with grease) and insert into all the injector receiving bores to a depth of approx. 45 mm. After cleaning each hole check that enough grease is on the drill to pick up fillings.​

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See page 41 of :​

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http://www.scatliff.mb.ca/pelican/MFI_Check_Measure_Adjust.pdf​

 

[boofs]

Thank you for your help and suggestion early 911

titleAndStar(974,0,1,false,"Register Secretary","")
Register Secretary,
The car runs superb and starts when warm/hot but wont start when warm/ hot and left for Half to one hour,
I have put the 2.11mm shin in between the thermostat and injector pump body and reset the idle adjustment but still got the not starting when hot problem,
although I do not think my injection pump with the enrichment and shut of solenoids should have the shim, I do not know what to try next, it is the fuel shut off from the injection pump to the injectors and I am running out of ideas what to do next, please some one help me this must have happened before, regards all.

 

[Laurence Gibbs]

early "mechanical " injection not my area but it does sound to me as though you are losing residual pressure in the injection pump causing vaporisation and problems when starting back up. Not knowing the system I would guess you want to check anything that controls residual pressure and warm running particularly any shut off devices, stats and even the injectors themselves. If the fuel pressure is allowed to leak away this will cause this fault. I am afraid I don't know the system well enough to say how this is acheived in this case.

 

[boofs]

Thank you for your reply Laurence Gibbs,
I also though it must be some form of losing residual pressure in the injection pump causing vaporisation, so I connected a wire from the enrichment solenoid 12volt supply terminal to the terminal on the 12volt solenoid on top of the fuel filter so as to squirt fuel into the intake funnels when cranking the engine when the no start problem occurs, this did make the engine fire up but only till the squirt of fuel was used up then the engine stopped This happened a few times untill the fuel in the injector pump came through to the injectors and then the engine ran OK,
I now no what the problem is but how to solve it is another matter any ideas from anyone as a recon injection pump is about £2000.00 (two thousand pounds UK).
Regards,
Tony.

 

[Laurence Gibbs]

Go through all the things that will lose pressure
check or get checked the
injectors
one way valves on the injection pump outlets
solenoid cut off valve (especially the closed position which can be adjusted!!!)
warm run stat
fuel lines and connections
Maybe best to have a chat with Autofarm, Tuthills or Mark from World Wide Classics who would be familiar with these engines and what fails on the pump.

 

[Ian MacKay]

There is a pressure control valve mounted inside the fuel filter mounting plate on the output line to the injector pump. As I understand it this is in place to ensure about 2 bar pressure infeed to the injector pump. It is worth checking that feed pressure.
Given where you live have you consulted Crispin Manners, he knows these engines.
Ian MacKay