excellent way to test injectors on 78 911

[stormcrow]

For those of you who want to test your injectors, I found an excellent way to do it. Go to your local mega store and purchase six 8 oz plastic baby bottles with nipples. Cut the top of the nipple off and you can insert the injector into the bottle.

You can visually inspect the flow pattern, check for injector leaks and time the flow rates and make a comparison to the other injectors.

The best thing about doing it this way is you won't have to worry about fuel going all over the place because the nipple seals around the injector and if pressure builds up inside, it will let it bleed out.

SteveKJR

"A Porsche does more then just go fast in a straight line

Attached are some pictures

[WIL84911]

Cool!

Might be a dumb question but how's the actual test? Turn on the ignition? Then what?

[Gogar]

You can open up the airbox, take out the air filter, and reach in and push the sensor plate up.

[al lkosmal]

Not a bad way to do that.

Can i ask you what kind of fuel lines you're using? and where you got them?

regards,

Al

[stormcrow]

To do the test the first thing to do is disconnect the CDI box otherwise you will destroy it. Once that is done, remove the red relay and insert a jumper between 87a and 30 pins on the bulkhead plug. This is typical for my car to jump out the fuel pump. Yours may be different so make sure you check

Next turn the ignition switch to the on position so that the gauges light up and the generator light comes on. Do not turn it to the start position As soon as the ignition is turned on you should hear the fuel pump running.

The next step is to inspect the injectors for leaks. With the fuel pump running, inspect the injectors for drips or leaks. After you complete this inspection, lift the air sensor plate and you should see fuel flowing from the injectors.

You can see the spray pattern on each injector to see if you get a nice cone pattern. That's pretty much it.

Hopes this answers you question.

SteveKJR

"A Porsche does more then just go fast in a straight line"

[stormcrow]

Those fuel lines came off a VW Jetta I believe. I happen to be at a junk yard and noticed that the VW Jetta has the injection system similar to ours so I managed to salvage some parts off it.

I also salvaged a pressur regulator and it is presently installed on my engine.

SteveKJR

"A Porsche does more then just go fast in a straight line"

[al lkosmal]

Steve,
I will be headed to the VW Jetta junkyard soon.

While i was doing the resto on my 71, I wanted to be able to clean and test my MFI injectors. I searched and found a little company 30 miles North of me, in Bellingham WA., making these simple testers for Mercedes (Bosch) injectors. They worked for my Porsche MFI injectors and for my 77S CIS injectors, as well. You can see at what pressure they pop open, watch the spray pattern, see if they drip.....clean them, etc.

[boyt911sc]

Originally Posted by stormcrow

To do the test the first thing to do is disconnect the CDI box otherwise you will destroy it. Once that is done, remove the red relay and insert a jumper between 87a and 30 pins on the bulkhead plug. This is typical for my car to jump out the fuel pump. Yours may be different so make sure you check

Next turn the ignition switch to the on position so that the gauges light up and the generator light comes on. Do not turn it to the start position As soon as the ignition is turned on you should hear the fuel pump running.

The next step is to inspect the injectors for leaks. With the fuel pump running, inspect the injectors for drips or leaks. After you complete this inspection, lift the air sensor plate and you should see fuel flowing from the injectors.

You can see the spray pattern on each injector to see if you get a nice cone pattern. That's pretty much it.

Hopes this answers you question.

SteveKJR

"A Porsche does more then just go fast in a straight line"

Steve,

Why would the CDI self destruct????? Running the fuel injectors with the CDI ON is part of the system and has been done by DIY'ers for years now. I've been running the fuel injector test for many years and never encountered such problem. Could you share your experience regarding the CDI with us? Thanks.

This is my baby food bottles tester version:

[stormcrow]

boyt,

It has been mentioned here on several posts that it should be disonnected. I guess it could be with the cdi unit not firing, it will generate internal heat and eventually destroy the transistor. That is my guess anyway.

SteveKJR

"A Porsche does more then just go fast in a straight line"

[stormcrow]

Al,

I like that test kit but I guess you could install the pressure gauge on the each injector and watch at what pressure it opens. Either way, both would be a good way to test the opening pressures on each injector.

SteveKJR

"A Porsche does more then just go fast in a straight line"

[T77911S]

lift the plate all the way up, the more fuel, the more accurate the test. i found a bad fuel injection line this way. it was only allowing half the fuel. i think it had been that way since new, unless someone replaced the lines and put the bad one on

[boyt911sc]

Originally Posted by stormcrow

To do the test the first thing to do is disconnect the CDI box otherwise you will destroy it. Once that is done, remove the red relay and insert a jumper between 87a and 30 pins on the bulkhead plug. This is typical for my car to jump out the fuel pump. Yours may be different so make sure you check

Next turn the ignition switch to the on position so that the gauges light up and the generator light comes on. Do not turn it to the start position As soon as the ignition is turned on you should hear the fuel pump running.

The next step is to inspect the injectors for leaks. With the fuel pump running, inspect the injectors for drips or leaks. After you complete this inspection, lift the air sensor plate and you should see fuel flowing from the injectors.

You can see the spray pattern on each injector to see if you get a nice cone pattern. That's pretty much it.

Hopes this answers you question.

SteveKJR

"A Porsche does more then just go fast in a straight line"

Steve,

The posting is a good one but you have some mis-information. And I don't believe that you have investigated or know for a fact that this is TRUE. There are a few guys in this forum who have extensive knowledge about electronics including the Bosch CDI and other brand names. You could check with anyone of them if you want to know or learn the facts.

The main reason I'm bringing this subject up is because this is a technical forum. People reading this information could be mislead to believe about what have you suggested. And would eventually continue to perpertuate another myth. Please accept my apology if I have offended you by contradicting a part of your post. The baby feeding bottle is a super idea.

Tony

[GaryR]

Hope it isn't true as my cold start died this spring and i've been giving a blast of fuel all year to get her started in the morning.. maybe I will fix it this winter.

[boyt911sc]

Originally Posted by GaryR

Hope it isn't true as my cold start died this spring and i've been giving a blast of fuel all year to get her started in the morning.. maybe I will fix it this winter.

Gary,

Why wait for the winter? Post a separate thread about the history and background of the problem. There are many members in this forum that would give you a good start to have this problem solved. Do you have a CIS fuel injection engine?

Tony

[GaryR]

Originally Posted by boyt911sc

Gary,

Why wait for the winter? Post a separate thread about the history and background of the problem. There are many members in this forum that would give you a good start to have this problem solved. Do you have a CIS fuel injection engine?

Tony

I'm just lazy Tony and the car is now parked and ready for the winter projects to get her ready for next years racing/DE schedule. I did post something (I think?) and got several ideas to test out, think I got as far as power to the yellow wire when cranking (?) and there was none, checked wire to the solenoid (was fine), and then said "Screw it, takes 2 minutes to pop the air filter and lift the plate for a quick squirt"..

[grantsmells]

i just tried this test on a couple of my injectors from my 2 cylinders that aren't firing (4&5) but i tested them one at a time.
anyhoo, with fuel pump running and not lifting the air sensor plate at all there was a noticeable amount of fuel coming out of each injector. cyl 4 slowly and in a nice spray, and cyl 5, faster and with a noticeable stream down the middle of the spray.
to me this says i need to get cyl 5 injector cleaned (will get them all done together) but does it also mean that there is something wrong with the injectors, letting fuel through with the air sensor plate closed? or would that be more likely a fuel distributer problem? i haven't checked any other injectors yet as it got dark, but i will tomorrow.

[timmy2]

They shouldn't be spraying any fuel with the metering lever on the rest position.
If system pressure is correct then they need to be repaired or replaced. A slight drip is probably acceptable, but a steady stream is no good.

[T77911S]

Originally Posted by timmy2

They shouldn't be spraying any fuel with the metering lever on the rest position.
If system pressure is correct then they need to be repaired or replaced. A slight drip is probably acceptable, but a steady stream is no good.

if the mixture is too rich they can "spray" or leak with the sensor plate at rest but you are right, no fuel should come out with the FP on and engine off.

[stormcrow]

Grant,

When you do the test you need to test all the injectors at once, otherwise raw fuel will be injected into the cylinders and that's not good.

As far as your test goes as previously stated those injectors are leaking and need to be cleaned to see if they can be salvaged or replaced.

[gazzerr]

Hey Guys, sorry I have a dumb question.

I have the hard metal lines - will they move around enough without damaging them to do this test?