Starting problems M10

[RoyvdenB]

Hello fellow E21 enthousiasts,
Recently I've bought myself a 1982 316. It has a 1.8i M10 engineswap done by one of the previous owners. The engine runs fine, but has a lot of problems starting when it's warm. My question is wether this is a common problem for these engines, and if so if there is a list of things that are the most likely cause of this ailment.

[Reck]

Do you know if it's k-jet or l-jet?

Found this with some googling... Dunno if you've already seen it though!

http://e21.tricord.be/e21/about/general ... erfaq2.php

Common K-Jet Problems and Recommended Solutions
Rule #1 -- If the car is running right and passes emissions, don't play with the fuel system. Keep the fuel circuit clean with a regular dose of fuel injector cleaner and drive the car. K-Jet when running properly is a very stable and reliable fuel injection system. The only problem is that it can be very sensative to subtle changes done by the tinkering type (yours truly).

Trouble Starting -- Although sometimes a rather vague question, this one seems to find its way into the forum quite a bit. There are many kinds of "starting trouble" and I'll try and break down a few of them here that we know the cause of.
Hot Starting -- "My car doesn't start when it sits for more than 30 minutes but less than 2 hours" i.e., the engine is still warm. There are two camps on this one.
Camp One: says the Cold Start Valve is malfunctioning. The CSV richens the mixture when the engine is cold, thus the name. If the engine is warm the CSV isn't really needed. In the event that it does function with the engine warm it can flood the motor.
Camp Two: says the Fuel Pressure Accumulator is bad. The fuel pressure accumulator is a diaphram at the rear of the car (near the fuel pump) that shuts off the fuel system when the engine stops. This blocking of the fuel line keeps pressure in the hardlines and all the other fuel lines in the car. If this unit fails the fuel slowly trickles back into the tank, leaving the fuel system dry. If the motor is still warm, the ECU assumes that there is still pressure in the fuel lines and does not turn the pump on immediately. Therefore you car tries to run on air (not going to do much).
Cold Starting -- There can be a few cold starting symptoms that are common.
"It just cranks and slowly catches" -- Here it most likely is the CSV. There isn't any other part of fuel system that IMMEDIATELY affects the way the car starts when cold.
"The car fires a few times and then slowly dies off" -- This is the WUR (warm up regulator). The warm up regulator has a bimetallic spring (much like a thermostat) that richens the mixture when cold. It is located on the drivers side of the motor below the starter. A very exspencive piece new, but some people have extras they are willing to part with or junkyard guys usually don't know how exspencive it is.

[RoyvdenB]

K-jet if I'm correct. Thanks for the info I'll look into it!

[opal green]

Hey Roy, I think I may be able to help.
If I would shut my car off warm, for more than 10 minutes. it wouldn't start.
I would have to wait until the car cooled before it would start again.
Turns out there is a check valve (non-return valve) on the outlet side of the fuel pump.
When this check valve fails, it allows fuel to return to the tank.
Residual heat from the engine heats the fuel in the injector lines and as the fuel expands and vapour is created, a vapour lock occurs. because the fuel is allowed to expand and to flow back into the tank.
The fuel pump works very hard to compress this vapour in the lines and can't get atomized fuel to the injectors for proper combustion to take place.
To prevent this, the system is designed to hold pressure between the fuel pump and fuel distributor.
I would think that the fuel accumulator would give cold and warm start problems.
It's function is to hold fuel under pressure and it is allowed to bleed down over time.
Cheap fix if it works anyway!

[RoyvdenB]

Thanks for the information! I'm having an expert look into it in a couple of weeks and I'll pass this information along to him.
Regards,
Roy

[Jeroen]

Otherwise place a few pics here so we know for sure what setup is under the hood!