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Me again! Fuel Injection systems

Black Beauty

Black Beauty

Member
Still got the same problem as my earlier thread, but something I don't understand is why does the engine stalls when I depress the throttle? There's no hesitation, just dies.

Where can I read up on how the injection system works in a '44 so that I can understand whats going on and how?

Ta
S

 
If it idles ok, but dies when you touch the throttle, my money would be on a worn out track in the airflow meter. Take the top off the airflow meter, you will see a copper U shaped arm which runs on a semi circular track... with the engine running, blip the throttle while watching the copper wiper arm.. if it does not move, your airflow meter is stuck... probably on a wear ridge inside the meter or a load of gunk.. clean it, unstick it and try again.. If the arm moves, (but the engine tries to die) apply some pressure to the U shaped wiper arm with the tip of your finger, causing a little more force to push it against the semi circular track.. blip the thottle again with your finger trying to follow the arm but without you applying enough force to hinder its movement... if it now revs clean you need to bend the arm by the tiniest amount to increase its pressure against the wiper track. This will slightly alter its contact point to a position where its running on virgin material which isnt worn out. other culprits... if it revs ok to about 1500 rpm, but dies after that point, its probably the throttle position switch has a stuck internal idle position microswitch. I have also seen crank sensors that will have a clean signal at idle, but a bad signal as the revs increase, to the point where the car will only idle... but my money is still on the air flow meter.
 
ORIGINAL: barks944 Does it idle ok?
Click to expand...
Yes, but she doesn't idle for long enough, perhaps 10-15 secs at most and then she just dies [:mad:]
ORIGINAL: Indi9xx If it idles ok, but dies when you touch the throttle, my money would be on a worn out track in the airflow meter.
Click to expand...
I took this apart some weeks ago and there is hardly any track showing, I suppose you'd expect that on a car of such low mileage. Indi - thanks for your other tips, but since she doesn't idle for long enough it makes checking things alot harder Having spent a few hours trawling Clarks forum pages as well as his technical notes, I am pretty certain its fuel starvation, or at least low pressure in the fuel rail or an issue with the one of the following , the fuel pressure regulator or the speed sensor. However, its just as likely to be something else [8|] Has anyone manufactured the jumper cables to bypass the DME relay? Does it work?
 
Had a half day today so, after put little one to bed, I took the DME out and replaced it with the jumper cables and automatically the pump started and presumably the injectors as they where making a noise. However, she still started first time and then died after a few seconds, tried it a few times and still the same. So, with the jumper cables removed I checked the voltage and resistance of the injectors, AFM and all seemed ok, Then I took off the end cap on the fuel rail without depressurising the fuel system, - the Haynes manual and clarks say that you must depressurise this otherwise fuel will spirt everywhere and.... all I got was a few dribbles, quite regular but nonetheless dribbles. Is this normal? Afterwards I put everything back again and put the jumper cable back in and i took off the vacuum hose at the top of the fuel pressure regulator as Haynes said that the pressure should increase inside the fuel rail but again she stalled. I also checked the afm in terms of movement/contact and again she died. A penny for your thoughts, related to the above of course[;)], because I am running out of ideas other than to randomly start replacing items. BB
 
You can attatch a hose to the end of the fuel rail run it to a bucket and start the fuel pump up. There are some flow rate figures for how much it should pump in a give time period.
 
A couple of weeks back, I did the pressure test with an old coke bottle and an innertube and a few cable ties, a bit heath robinson but it went well until the pressure in the rail began to build up and the inner tube began to expand, quite quickly I might add. Fortunately I disconnected the battery before it got messy. But flow rate was spot on. So after a long and protracted session I found that the reason she would start but then die after a few seconds, was due to the AFM - there's a brass arm which extends up from the electrical connector and it should touch another brass contact however they weren't touching. As soon as I touched them together it ran smoothly. So you can imagine the grin on my face, Cheshire cat springs to mind. Now, I'm back to my misfire, which doesn't happen all the time but when it does, she feels lumpy and won't pull, its like shes running on 3 cylinders but I'm sure it is 4, just feels like 3 and to top it off she won't restart when hot ? Grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr [:mad:] [:mad:] [:mad:] [:mad:] [:mad:] [:mad:] [:mad:] If she doesn't misfire, she restarts when hot - go figure!
 
I'm sure I read something about overpressure on the fuel rail causing miss firing. Apparently the high pressure differential can cause high current on the injectors and the DME might shut some of them off or something causing missfire. If I understand correctly the test you did only tests the pump flow rate so a problem with the pressure regulating system could still be present.
 
Just had a thought. I had a similar problem to this a while ago the car would crank over then cut out almost straight away. I finally worked out that I had cracked a vacuum pipe when moving the mannifold. This caused a vacuum leak. I replace the pipes and checked all the connections and it started first time. If you find you need pipes let me know as my dad makes hoses and made the new ones I used. He wouldn't want much for doing it. Probably like 3 quid a pipe or somthing.
 
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