Stuttering when accelerating under load

[Nick H]

Took the car out for a run at the weekend. I noticed that it was stuttering/jerky under acceleration. 
 This happens when under load. Engine will happily rev smoothly when in neutral.
Car starts fine and idles smoothly when hot or cold.
Stuttering seams to smooth slightly if I floor the throttle or disappears completely if I apply throttle very slowly.
Anyone have any ideas? I tried a tank of super unleaded but still have the issue today.

Thanks
Nick H

[priesh]

I had this exact issue when I got my car. Turns out mine was a knackered rotor arm and loose distributor cap (one of the clips had broken). I replaced the arm, cap, and clip (also replaced leads and plugs while I was there) and that sorted it. For me anyway.

Could also be fuel filter? Or the hose coming from fuel tank needs internal reinforcement?

[Nick H]

Thanks Priesh,
                     I was thinking fuel pump but I upgraded to the new Special T style last year. Took another good look around the engine bay tonight before committing to some fuel tank diving. Found a vacuum hose had come off  doh! Problem now fixed   

Nick H

[priesh]

Great! Glad you found the issue

[TheScAtMaN]

Hi Nick, did this actually solve the problem for you or was it the replacing of the metering head and swapping back to the old fuel pump that did it?
Having a similar problem but think it's fuel pump on mine:
http://www.deloreans.co.uk/forum/showthr...p?tid=5858
Was considering the Special T type but have concerns if yours seems to have failed so quickly.

[Nick H]

My current thinking is that it was a combination of factors.
However from my experience I would try the fuel pump first.
Also check the pick up pre filter in the tank. Also take a look at the RPM relay.
To give you a real idea what’s going on with the fuel injection system you really
need a pressure test gauge. However this will cost £50-£100 as I had never touched the
system apart from new filters and accumulator over nearly 20 years. I just decided
all the parts were suspect and to just put the money towards renewing the lot.

The item that most improved the running of the engine was a new CPR.
Waiting for some new bits for the fuel tank, hopefully sort it this weekend.
I would steer clear of the updated style fuel pumps and install the original style but add a spring
inside the fuel pickup hose. Watch Martin G’s YouTube vid of how to install the pump
correctly.
Nick H

[Chris P]

I was talking to a very "knowledgeable member" the other day, who stated firmly that many on the "Improved" products turn out to be anything but. Staying stock has a lot to recommend it.

[Nick H]

Hi Chris,
I have to say I’m inclined to agree . I just finished putting the original fuel pump back.

I have done a bit of research and found the unit used as a base for the new style fuel
pump. The original non modified version is only 60psi pressure.
There’s a video on YouTube of a guy fitting one to his DeLorean and surprise surprise mentions
he is having hot starting issues afterwards.

Also never take for granted that you put back things as you find them. Someone could
have been there before. Case in point the metal return pipe in the tank on my car was 
a previous owner botch. Never spotted it until I compared it with Martin’s how to video.
Also the two bumps in the tank that locate the pickup. I originally put it back years ago when I replaced the pickup hose and filter, how I found it. Wrong!      

Good news, hot start problem fixed. 


Nick H