jonnyoutram

hi, im nwe to this game... just bought a 1984 500 sec, had many many problems most have been fixed for example the notorious high idle problem!!


my last main problem is a miss fire!

the whole ignition system is new...

plugs
leads
distributer rotor arm
idle controll unit.....

then

fuel filter
oil
air
cleaning of k jet fuelling system

this was all done by a mechanc friend of mine and has solved allot but there is still an obvious problem


we think its either the injectors or the k jet fuelling system

i have spent £2000 so far restoring the car and need to be carefull with money now..

the symptoms are:

lumpy idle

lumpy pulling away

clears up just below 2000 rpm on acceleration

trouble starting needs gas pedal(does this suggest leaking injectors??)

what should i do any ideas??

thanks everyone

Yacht Master

Vacuum leak, the injectors sit in a plastic cups and over time they get brittle and crack and allow a vacuum leak. The same is true of all the hoses you need to check everything. I would suggest that you take a pic if the engine and hose locations before you start to sort it out. Your mechanic should know how to find a vacuum leak with WD40 spray, this is an easy way to find leaks on the manifold and injector cups, inspect the idle circuit hoses for cracks and poor fit on connectors. The 126 SEC is one of the best cars ever built.

Untertürkheim

Trouble starting can be the fuel pressure regulator valve (I believe that is what it is called), also may be called the check valve. Basically, on the fuel pump, a one-way valve that is supposed to maintain fuel pressure in the system when the car is shut off. If this valve or the fuel pump is going bad, pressure will leak out of the system and the car will be hard to start when it has beeen sitting.

jonnyoutram

a leak was found and repaired vacume system pressure fine now, the problem was still there. i have not taken any of the injectors out yet.. do you think its worth taking them out and checking the plastic cup??

how can i test that fuel pressure regulator valve??

thanks

Untertürkheim

First, does the hard starting become more or less apparent depending on how long the car has sat since being shut off? If it gets worse with time, then this may be the culprit.

One way of course is to hook up a fuel pressure gague and watch the reading while the car is running, then watch the pressure when the car is shut off and see if it continues to drop over time.

The other, non-scientific way to test it would be to basically prime the fuel lines before trying to start the car and see if anything is better or worse. To do this, turn the key from off to position 2 (run) for 3-5 seconds, repeat 20 times or so before actually trying to start the car. Since the fuel pumps run for a couple seconds in position 2 before the car is started, doing this enough should build up enough fuel pressure to tell you if it is an issue.

jonnyoutram

yes the car starts much better when it has been running and the longer u leave it, the worse it gets...

i tried your method of the 20 times priming thing, it didnt seem to make a differeance.. i dont have a fuel pressure gague.

someone suggested that the lumpy idle and bad starting would be because the injectors are broken and leaking fuel into the cylinders when the car is left, therefore fludding the engine before u even try to start the car...

does this sound like it could be true?

do u still think it could be this fuel pressure regulator? should i try to get hold of a pressure tester??


thanks so much for the advice!!!

jonnyoutram

is it easy to check the injectors?

is there any way i can check if they are the problem before taking them out??

i have been told it could also be the k-jetronic system thing that sits on top of the throttle body, i noticed someone was saying on another thread that they had to change a valve thing in it to sort a similar problem...

wondering what to do first, should i just take the injectors out and have a look??

what are the signs of them being broken?? or these plastic caps being broken,.. is it obvious?

sorry for being so confusing and difficult.

thank you so much for the advice