Hi all,
i am slowly working on my 1978 Daimler V12. The car has a surprisingly good body, interior (sagged headlining) and silver paint. It had totally rotted out fuel tanks.
Mechanically I have found numerous small problems with the engine including a misplaced valve shim resulting in a riding valve, jammed auto advance in the distributor, failed vacuum advance and a generally disgusting appearance in the engine bay. The car's paper work indicates it is relatively low mileage (130k).
When I ran the engine it had no nasty sounds, good oil pressure etc but was running very poorly, missing on numerous cylinders.
I tested the injectors with a test bed I made up and found 4 injectors not working at all. The remaining 8 delivered a very poor spray of fuel which is improving with further operation, running a mixture of fuel and injector cleaner through them.
I believe that 20 years of stale fuel has clogged the injectors.
The 4 Inoperative injectors don't even give a click when they receive a pulse from the test unit. I have tested their continuity with a multimeter and it is similar to the injectors that are working. From this I conclude that they are not burnt out.
i have a cheap ultrasonic cleaner.
Questions
# Am I correct in thinking that stale fuel could totally gum up an injector to point where it doesn't even click?
# What course of action should I take to attempt to get the failed injectors to work?
# What medium should I use in the ultrasonic cleaner to clean the injectors. I was thinking of pure injector cleaner?
# What common mistakes am I likely to make?
# Would leaving the injectors soaking in any liquid be of advantage?
# Is Avgas useful as a cleaning agent.

Any tips or suggestions gratefully recieved

Alan

 

I think you are on the right track and correct about gummed up injectors. I've revived these old injectors by removing the plastic pintle covers and carefully exercising the pintle manually with a sturdy plastic tweezers. Then they can be cycled with electricity and cleaned normally. The pintle cover may break while trying to remove it but its not necessary for proper intermittent operation and the covers are replaceable.

When you do get it running you are going to be amazed how fast these engines can drink fuel.

 

Hi icsamerica and all,
yesterday due to appalling weather I got back into the workshop and to the injectors.
I put them in my ultrasonic tank with a solution of water and very strong detergent and gave them numerous ultrasonic cleaning cycles.
i had previously made up a test bed consisting of a a small fuel tank (4lt fuel container), filter, pump, pressure gauge and pressure regulator. I made up a 50/50 mixture of fuel and injector cleaner.
I connected the injector tester (a small unit advertised widely that appears to work very well) and retested the injectors. Initially 4 of the 12 were totally dead.
One of the gummed up injectors started to work almost straight away, starting with a dribble and slowly improving to the desired spray.
The other injectors displayed various levels of difficulty in unclogging.
As suggested by icsamerica (thank you) I was able to remove the plastic cover from the nozzle and very gently manipulate the pintle valve that protrudes. It is surprising how tightly they were glued closed. With patience they would start to move. Initially they would jam into the open position with a solid stream of unpulsed fuel squirting forth but slowly the pulsed spray was restored.
I am very pleased to have discovered why the engine was running so poorly after awaking from a score of years slumber and having the injectors working again.
I shall reassemble the manifolds etc ( much plumbing and wiring connections I am not looking forward to) and see if I can get the old girl running on 12 of the 12 cylinders. From then on I look towards getting her back on the road.
Again, thank you to the icsamerica and the forum in general for the advise. I would not have known that the plastic end was removable that allowed me to access the valve without your advise
alan