Engine cranks but won't start when hot

[Velum]

Hi!

Can anyone help me with this one. The engine of my Porsche 914 2.0 L 1972 (1973 Engine; Fuel Injection) will crank, but won't start if the engine is hot. When the engine is cool, it starts no problem. However, if I derive for, let's say half an hour, and I stop the engine, it won't start anymore until the engine is cold again. That is a couple of hours later. Does anyone have a clue of what could cause this?

Added on June 24: I forgot to mention that when the engine is hot, it will start on compression, even though it is not starting with the starter.

Best regards,

Jean-François Beauchamp

[nine_one_4]

It could be vapor lock where the fuel in the hot fuel lines starts to vaporize. It's not an uncommon problem in hot temperatures.

[Tobra]

Check your timing, valve clearance

[trekkor]

I had this problem as well.

It wouldn't fire off while cranking, but if on a hill, it would bump start after rolling a bit.

Try holding you foot to the floor while cranking. give it 20 seconds.


KT

[nine_one_4]

The factory relocated the fuel pump to the front trunk in '75 to solve the hot start problem. Here's a Pelican technical article that describes how to do this relocation and here's a pic of page 45 in the Haynes manual showing both factory locations for the fuel pump.

I also found this technical article from an old issue of VW/Porsche that describes moving the pump to a location near the steering rack.

(Click picture to get larger version)

[teenerted1]

dont put your foot to the floor!!!!!!!

just keep cranking. it will evenually kick in.

yes you are getting the usuall problem with the rear fuel pump getting hot.

[RandyLok]

If it's vapor lock, why does push starting work?

[John Rogers]

I agree with the vapor lock possibility. You could put on a fuel pressure gauge and watch to see what it does for pressure when the engine gets hot. We used to have that problem with our 1974 D-jet and I put in a gauge and just left it in.

[Velum]

I've had the car for ten years, but I've only had the problem for two years. According to my temperature gauge, the engine is not running hotter than before. I changed my heat-exchangers a few years ago for stainless steal ones. Do the generate more heat?

Also, I'm living in Montreal, so it gets hot in the Summer, but we have cool days too. I'll have to check whether the outside temperature is having an effect.

As someone was asking earlier, I'm also wondering why the car is starting with a push-start.

Cheers! And thanks for all the suggestions!

JF

[pbanders]

If you have vapor lock (unlikely - I have a stock 2.0 injected setup with my fuel pump in the engine compartment, and I've never had vapor lock - and I live in Phoenix, AZ), it won't start because there's no supply. Try using starting fluid to verify. If you give it a squirt and it starts, you're lean.

More likely, you're too rich due to one or more leaky injectors. The residual pressure in the loop is relieved through the leaky injector into the cylinder, flooding the motor. To check, try the following. With the key in the off position, depress the accellerator pedal to the floor. Now, turn and crank for 20 seconds. If it starts, it's likely you were rich and the extra air from the WOT gave you a mixture that would fire.

[John Rogers]

I missed the point about the car starting warm if you push it. Sounds like the voltage (12 volts) to the coil could be too low when cranking if the engine is hot. With the key on the voltage would be higher so the starter could be causing a large drain in power. Try a volt meter across the coil terminals when hot with switch on and when cranking? As mentioned if you give it a shot of instant start or ether it should fire even with a very weak spark.

[youssuf69]

hello.
I am having serious problem with my car mercedes c220cdi (w204) NEED HELP PLEASE.
car start and drive very well when its cold then after more than 1 hour drive its misfire or hesitating even turn off while driving.
but when the engine goes off when i start it does start normal.

I had the car diagnose several times and its come up with (oil temperature sensor ) which I replaced but fault still here and again on diagnostic it kept coming on (oil temperature sensor)
Now I am randomly changing parts which I replace Crankshaf sensor and Camshaft sensor but fault still happening.

Note that this fault is happening only after driving more than 1 hour OR if I leave the car on idle 1 hr 30mins.

please help.
thanks
youssuf

[dr914]

you may want to check the head temperature sensor

[Dave at Pelican Parts]

Youssuf, I suggest you check out the Mercedes tech forums on our sister site, Peach Parts.

Mercedes-Benz Discussion Forum, DIY Technical Advice, Parts and Cars for Sale - Welcome to the PeachParts Forum!

They can probably help you a lot more with your Benz than we can; this sub-forum is specifically for the VW-Porsche 914.

--DD