Testing injectors on 72 350sl

[Mikesmerc]

I want to test the injectors to see if they are leaking, dribbling or fine spraying. Having trouble getting someone to check em in my area. Would it be possible to remove a bank of injectors complete with the fuel header, extend the fuel supply hose from the regulator so as they are out of reach of the engine bay. Hook up a remote 12v battery to each injector via a remote switch. Turn on the ignition and pressurise the system, flick th switch and see if the connected injector sprays correctly. You should also see if any are leaking.
Is all of the above rubbish or should it work?
Thanks for any replys.
Rgds
mike

 

[Myros]

it makes theoretical sense

but I'd get the fire extinguisher handy, and have a friend around to beat the flames off me as well.
Does yours have the D jetronic? It's just that I have the (german) manual for the KE, if I could help with any info.

 

[996jimbo]

I guess you'd need to know first what voltage / ampage the injectors operate on and whether a sustained voltage (rather than pulse) straight off a battery would knacker them. The system may not pressurise sufficiently for a sustained opening also. Plus just looking at what comes out probably wouldn't tell you much (assuming it worked at all) about the state or quality of the spray. And if you do it with petrol you'd be firing out a rather explosive mixture.

Surely there must be an easier way.

Still, it sounds like fun to try - fire extinguisher on standby!

 

[Mikesmerc]

My cigarette and I promise to stay up wind of the injectors.:wink:
Think its D Myros, no fuel distributor. I presume the voltage will be marked on the injectors. Open to any other suggestions.Haynes Manual not very helpful
Mike

 

[Myros]

Ah well

couldn't tell you about the voltage. Sounds like it's definitely D. Careful with the hoses, they are very sensitive to kinks, so I hear.
I know Bosch were very keen on continuous injection in the early days, K-jet being just that. L-jet was different, and not as good in some people's opinion.
Not that that helps you any. I wouldn't be surprised if it were some continous rather than a pulsed type of injector. I suppose proximity to the head is a good guide. Any advantage of a pulsed injector would be lost the further away from the combustion chamber it is, and I believe the converse true on a continuous type. Although the distances involved would be small anyway. Oh stop it, I'm confusing myself now.
Good luck

 

[Mikesmerc]

Myros there are trigger contacts under the base of the distributor which sends pulses to the injectors, so it seems not to be continous.
Cheers
Mike

 

[Myros]

that's ok then

the dizzy triggers the pulse, and the throttle varies the pressure, and therfore amount delivered. elegant. Sounds like you'll be cranking the engine a bit. Try and have someone video it, so you don't end up soaking the emerald isle with super unleaded.

 

[996jimbo]

If you hear:

HisssssssssssssssssssssWHUMPF!

it suggests a slow burn and the particles are not coming out fine enough - injector a little clogged

If you hear:

hisssssssssssssssssssssKABOOM!

then your injector was sending out a nice fine spray.

You might want a friend nearby to make a note and let you know what the noise was when you get out of hospital.

 

[Mikesmerc]

Jimbo, have you no faith whatsoever in my stupidty, very offputting or is that what you are mildly hinting at...?.
Have to check throttle position sensor as well Myros, as I thing shes starved of juice, hence the the above mentioned brain wave with the injectors. If you dont hear from me in the next few days...weeks send me a get well card.:mrgreen:

 

[996jimbo]

Jimbo, have you no faith whatsoever in my stupidty, very offputting or is that what you are mildly hinting at...?.

I'm sorry, I just can't get the image of the whole procedure out of my mind, and every time I think about it it ends with a mighty explosion!

You'll be pleased to know I make no claims whatsoever to be clairvoyant. Indeed, I've never won on the national lottery and always miss my train.

 

[pascal]

Mike

Let me no when. Just in case I visit Cork in the next few weeks.


Ps: Put flame retardent on your ebrows.

 

[Myros]

I'd invest

in some flame-proof pampers as well. Good luck Mike, we'll keep watching the news.

 

[Mikesmerc]

No news yet, only took apart the throttle position sensor tonight for a look see at the condition of the contacts, all looks very well indeed, like new in fact. Perhaps over the weekend I will give the injectors a blast... err test, you should see the mushroom cloud from where you are Pascal. Any better ideas on testing the injectors before this will be appreciated if only to prevent me from claiming for fire damage from my insurance company:mrgreen: .

Regards
Mike

 

[996jimbo]

Take them out and have a look at them?

 

[Mikesmerc]

Will do that but I would imagine it wont tell me much about their operation. Read on another post about using compressed air and a hose filled with white spirit. An electrical pulsed applied to each injector and this is supposed to clean em out. Just as flammable I would imagine.
Mike

 

[Mikesmerc]

Fiddling around with the SL tonight I decided to check the fuel delivery pressure with a tester I got for my 560SEC that has the Ke jetronic injection system. Found the fuel hose which seems to serve a primary regulator then a secondary regulator which splits into two to serve each bank of cylinders and each header is linked with a hose at the front of the engine. Doesnt seem to have a return fuel pipe which I think is a bit odd. Hooked the guage in between the delivery pipe and the first reg., turned the key to prime the system and nothing registered on the guage. Started the motor and left her idle and registered only 10psi. Checked the vague haynes manual and it said that fuel pressure at idle should be around 80 Psi. Is this my problem or has some butcher dissconnected the fuel return pipe or am I simply testing at the wrong location? Any advise from anyone familiar with this injection system gratfully appreciated.
I might just post a new topic regarding this new discovery/problem of mine.
Thanks everyone for your helpful and funny comments.
Mike