Dripping Injectors CIS - Test at System Pressure?

strictly · 07:25 AM

1978 911 ROW 3.0 SC

NEW Bosch Injectors -Dripping

I have just replaced the injectors (new bosch). Before actually putting them in the injector holes, I am testing them (everthing else connected), and 3 of the 6 new are dripping, with the FP running (not on same side of engine). I do question my fuel distributor, but wanted to start with the injectors.

I know this has been covered before (back off mixture screw, etc). My question is this

Q To test the injectors, do I do so as follows :

1) set up CIS tester for system pressure (valve closed, engine off, FP running). My System pressure is 69 PSI (4.75 Bar).
2) then all injectors in a pot, push up on air flow plate until i get flow, then let go of plate, and observe each injector for dripping.

Is it possiable the 70 PSI is too much pressure for the injectors? and therefore I should be testing them with the valve open as in for control pressure/WUR where the pressure is lower?

I noticed i am having dripping with the FP running, but when the FP is stopped, the residual pressure stays at 69psi (for a while before dropping to 0, over 1 hour), and the drips stop after a short while, with the FP running, the drips are constant. The engine has been completly rebuilt (not yet run) so i wanted to check before i bore wash it with fuel by accident!

Luke

P.S once i understand if i am doing it right, I will then play with the mixture screw.

boyt911sc · boyt911sc's Garage

Luke,

The range for system fuel pressures (CIS) is 65~75 psi. I like to set the system fuel pressure @ 72 psi. The system fuel pressure has nothing to do with your leaking injectors. The fuel injector is leaking because;
a). The fuel injector is defective and leaking.
b). The fuel injector is good but the FD is leaking.

Remove the fuel injector/s and test run the FP. There should be no fuel delivery at this point. And if there is, either the FD is leaking or the mixture setting is set too high or the FD plunger is stuck and not sitting down at rest. Next, install the injectors for the test for the fuel line/s that is not leaking. Lift up the sensor plate and allow fuel to run for a couple of seconds and release the sensor plate. There should be no dripping after you let the sensor plate off. Keep us posted.

Tony

T77911S · 09-21-2016, 10:11 AM

could also be that the mixture is set a tad on the rich side and they are the first ones to spray.
(just saw tony posted the same)

you could also swap injectors around.
I would also do a flow comparison since you are this far into it.
put each injector in its own container and lift the sensor plate to flow fuel. the more fuel the more accurate the test.

strictly · 11:03 AM

Quote:

Originally Posted by boyt911sc

Luke,

The range for system fuel pressures (CIS) is 65~75 psi. I like to set the system fuel pressure @ 72 psi. The system fuel pressure has nothing to do with your leaking injectors. The fuel injector is leaking because;
a). The fuel injector is defective and leaking.
b). The fuel injector is good but the FD is leaking.

Remove the fuel injector/s and test run the FP. There should be no fuel delivery at this point. And if there is, either the FD is leaking or the mixture setting is set too high or the FD plunger is stuck and not sitting down at rest. Next, install the injectors for the test for the fuel line/s that is not leaking. Lift up the sensor plate and allow fuel to run for a couple of seconds and release the sensor plate. There should be no dripping after you let the sensor plate off. Keep us posted.

Tony

Hi Tony,

Thank you for that. I have read alot of your posts, and was hoping you would chime in =)

Ok I am going to completely remove the injectors, i forgot i had read you said that on a different topic. And see what the results are, with the AF plate at rest. If the FD is good then there should be no flow (FP running of course).

If there are no leaks/dribbles, then reinstall the injectors, lift up the plate (FP running) and release, and if now leaking/dribbles, then it must be in the injector (right?).

Could i do the same test WITHOUT the injector attached, i.e lift up an release - it should flow and then stop right?

For this test, is the CIS tester connected? If NOT supposed to be connected, if i had the CIS tester in the CONTROL control setting (valve from FD to WUR open), this is basically the same as the tester not being there right (?)

Luke

strictly · 09-21-2016, 11:00 AM

Quote:

Originally Posted by T77911S

could also be that the mixture is set a tad on the rich side and they are the first ones to spray.
(just saw tony posted the same)

you could also swap injectors around.
I would also do a flow comparison since you are this far into it.
put each injector in its own container and lift the sensor plate to flow fuel. the more fuel the more accurate the test.

Great idea, that was next on my list, I have done a "quick" flow test (3 injectors in each container), same flow, BUT I will do a 6 individual injector flow test as a next step after the test with no injector at all. - in the flow test, would max flow (sensor plate at highest point) for say 2 minutes be enough? Does it matter if the WUR is cold or hot? I'm going to guess and say it dosent, as the WUR cold/hot just allows the FD to deliver more fuel to the injectors, and if i am holding the plate at full height, then we are just measuring flow

------ Mixture ----

Good idea on the mixture, i just read in the Porsche Workshop manual, that an basic setting for mixture is to turn the screw until the injectors just flow, then back off (Anti Clockwise) by 1/2 turn. The when engine warm check with CO meter. So i could for example to start not back off the full 1/2 turn and expirement.

gazzerr · 09-21-2016, 02:20 PM

Sounds like the base mixture setting is too high. You're supposed to go clockwise until they just start ejecting then wind it back half a turn and that's your base.

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by strictly

Hi Tony,

Thank you for that. I have read alot of your posts, and was hoping you would chime in =)

Ok I am going to completely remove the injectors, i forgot i had read you said that on a different topic. And see what the results are, with the AF plate at rest. If the FD is good then there should be no flow (FP running of course).

If there are no leaks/dribbles, then reinstall the injectors, lift up the plate (FP running) and release, and if now leaking/dribbles, then it must be in the injector (right?).

Could i do the same test WITHOUT the injector attached, i.e lift up an release - it should flow and then stop right?

For this test, is the CIS tester connected? If NOT supposed to be connected, if i had the CIS tester in the CONTROL control setting (valve from FD to WUR open), this is basically the same as the tester not being there right (?)

Luke

Luke,

What did you mean 'CIS tester'? If you meant pressure gauge, you could leave it connected or installed with the valve open similar to checking control fuel pressure. With the FP running, a good FD will not deliver fuel to the fuel lines/injectors when the plunger is down (at rest). Just in case, place the ends of the fuel lines (no injector) into containers to collect any fuel that might come out unexpectedly. Lift up the sensor plate to test delivery flow and release. There should be no fuel coming out after you release the sensor plate.

Repeat the above test with fuel injectors installed. Lift up the sensor plate for 1~2 sec. and release. There should be no drips when you release the sensor plate. Replace defective or leaking fuel injectors.

Tony

ossiblue · 09-22-2016, 07:06 AM

Quote:

Originally Posted by boyt911sc

Luke,

What did you mean 'CIS tester'? If you meant pressure gauge, you could leave it connected or installed with the valve open similar to checking control fuel pressure. With the FP running, a good FD will not deliver fuel to the fuel lines/injectors when the plunger is down (at rest). Just in case, place the ends of the fuel lines (no injector) into containers to collect any fuel that might come out unexpectedly. Lift up the sensor plate to test delivery flow and release. There should be no fuel coming out after you release the sensor plate.

Repeat the above test with fuel injectors installed. Lift up the sensor plate for 1~2 sec. and release. There should be no drips when you release the sensor plate. Replace defective or leaking fuel injectors.

Tony

Question for you, Tony.

Don't want to high jack, but this is for clarification/education for me and, hopefully, the OP.

If the injectors are removed and there is no fuel coming from the end of the lines when the plate is at rest, why would a leak develop once a bad injector was added to the end? There is no fuel coming from the FD, as per the previous test. Is the drip simply the fuel that remains in the body of the injector? A leak at the injector indicates the injector does not "seal" completely, correct? Does this failure to seal allow the vacuum of the cylinder to pull fuel into the engine through the lines and FD and that's why there are running problems?

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by ossiblue

Question for you, Tony.

Don't want to high jack, but this is for clarification/education for me and, hopefully, the OP.

If the injectors are removed and there is no fuel coming from the end of the lines when the plate is at rest, why would a leak develop once a bad injector was added to the end? There is no fuel coming from the FD, as per the previous test. Is the drip simply the fuel that remains in the body of the injector? A leak at the injector indicates the injector does not "seal" completely, correct? Does this failure to seal allow the vacuum of the cylinder to pull fuel into the engine through the lines and FD and that's why there are running problems?

Larry,

I don't explain well as you do and I will try again for clarification. The first part of the test is to run the FP with the injectors removed from the fuel lines.
a). If the FD is not leaking (internal leak), there should be no fuel coming out from the fuel line/s.
b). Each of the six (6) fuel ports for FD has individual seal (o-ring) and could go bad or defective or wrong size.
c). So any of the fuel lines that does not leak during the test is considered good and could be used to test fuel injector/s' operation.
d). Any fuel injectors installed at a particular line (tested OK) that leaks after a flow test is considered defective or bad. NOTE: You need to flow test the lines from FD by lifting the AFS without injector installed first, then put the injector for another flow test.
d). Injector spray patterns are tested differently. They involved more than just looking at the mist like spray patterns. You have to consider the operating or opening pressure of individual injectors.

Before you test an injector for drips or leakage or spray patterns, it is imperative that this particular fuel line is connected to a good fuel port from the FD. For example: If a particular fuel port (FD) has a defective o-ring and is leaking, fuel will be prematurely delivered to the fuel line and injector even if the plunger is at rest (down position). Did I explain this well enough to be understood? Please let me know. Thanks.

Tony

Charles Freeborn · Charles Freeborn's Garage

Be certain that the air flow cone / plunger is seating correctly. If there is no air flow, the plunger should be bottomed out and the system will pass no fuel. If it is seating correctly and there is still fuel flowing, you've got an issue with your FD.

ossiblue · 06:22 PM

Quote:

Originally Posted by boyt911sc

Larry,

I don't explain well as you do and I will try again for clarification. The first part of the test is to run the FP with the injectors removed from the fuel lines.
a). If the FD is not leaking (internal leak), there should be no fuel coming out from the fuel line/s.
b). Each of the six (6) fuel ports for FD has individual seal (o-ring) and could go bad or defective or wrong size.
c). So any of the fuel lines that does not leak during the test is considered good and could be used to test fuel injector/s' operation.
d). Any fuel injectors installed at a particular line (tested OK) that leaks after a flow test is considered defective or bad. NOTE: You need to flow test the lines from FD by lifting the AFS without injector installed first, then put the injector for another flow test.
d). Injector spray patterns are tested differently. They involved more than just looking at the mist like spray patterns. You have to consider the operating or opening pressure of individual injectors.

Before you test an injector for drips or leakage or spray patterns, it is imperative that this particular fuel line is connected to a good fuel port from the FD. For example: If a particular fuel port (FD) has a defective o-ring and is leaking, fuel will be prematurely delivered to the fuel line and injector even if the plunger is at rest (down position). Did I explain this well enough to be understood? Please let me know. Thanks.

Tony

Yes, your explanation is very clear, but it doesn't really answer my question so let me rephrase it.

If you test a fuel line as you describe above, and no fuel leaks out once you lift the plate and then return it to its stop (flow test), the line and its corresponding FD port is good, correct?

My question is, why would a bad injector--added to a non-leaking line--cause a leak since, from the flow test, the line does not leak? If fuel doesn't leak from a line after a flow test without an injector, what would make it leak once the injector is added? Is it because when an injector is added, the line remains pressurized and the fuel is not stopped by the seal in the FD but rather the mechanics of the injector?

Have I got it? Now, back to the OP's issues. (Sorry, strictly)

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by ossiblue

Yes, your explanation is very clear, but it doesn't really answer my question so let me rephrase it.

If you test a fuel line as you describe above, and no fuel leaks out once you lift the plate and then return it to its stop (flow test), the line and its corresponding FD port is good, correct?

My question is, why would a bad injector--added to a non-leaking line--cause a leak since, from the flow test, the line does not leak? If fuel doesn't leak from a line after a flow test without an injector, what would make it leak once the injector is added? Is it because when an injector is added, the line remains pressurized and the fuel is not stopped by the seal in the FD but rather the mechanics of the injector?

Have I got it? Now, back to the OP's issues.

Larry,

When you test a FD, the things you have to verify or confirm are the following:
a). No sign of leak around the gasket or perimeter of the FD body.
b). All fuel delivery ports (6) where the fuel lines are connected do not deliver fuel when the plunger is down.
c). All fuel lines deliver comparable amount of fuel when you raise the plunger upwards.

Now, to answer your question about installing a bad fuel injector to a good FD or line, a bad or leaking fuel injector will always be bad whether you installed it to a good or bad line because it is confirmed BAD. A fuel line or port that is not leaking when the plunger is down and FP running means the o-ring is good and doing its job. This is where you get confused. The good line that does not leak will deliver fuel when you raise the plunger. And when you install a leaky (defective) injector to this line (good) the injector will still be bad or leaking after a flow test. A leaky injector is evaluated when the plunger is down or at rest.

In short, you perform a flow test to evaluate the injector or line or FD. A flow test is lifting or raising the FD plunger for delivery and then allowing the plunger to settle down to stop the fuel flow while the FP is running. I think you are missing or excluding about raising the plunger and allowing it to go down for the test.

Tony

ossiblue · 09-22-2016, 07:39 PM

Quote:

Originally Posted by boyt911sc

Larry,

When you test a FD, the things you have to verify or confirm are the following:
a). No sign of leak around the gasket or perimeter of the FD body.
b). All fuel delivery ports (6) where the fuel lines are connected do not deliver fuel when the plunger is down.
c). All fuel lines deliver comparable amount of fuel when you raise the plunger upwards.

Now, to answer your question about installing a bad fuel injector to a good FD or line, a bad or leaking fuel injector will always be bad whether you installed it to a good or bad line because it is confirmed BAD. A fuel line or port that is not leaking when the plunger is down and FP running means the o-ring is good and doing its job. This is where you get confused. The good line that does not leak will deliver fuel when you raise the plunger. And when you install a leaky (defective) injector to this line (good) the injector will still be bad or leaking after a flow test. A leaky injector is evaluated when the plunger is down or at rest.

In short, you perform a flow test to evaluate the injector or line or FD. A flow test is lifting or raising the FD plunger for delivery and then allowing the plunger to settle down to stop the fuel flow while the FP is running. I think you are missing or excluding about raising the plunger and allowing it to go down for the test.

Tony

Got it, thanks!

strictly · 09-23-2016, 11:01 AM

Ok guys, so ive done some tests. I have to say im fairly confused, before i talk about the tests, i will make an observation

--- observation

Ive noticed, while running the injector test, when i connect the FP (i.e do test, stop for a coffee, reconnect FP, then i get a "spurt" of fuel out of 4 of the injectors without touching the Air flow plate. I then turned the mixture screw a FULL turn ANTI clockwise, and no more spurts of fuel, but the injectors were dripping, i also tried a different accumulator, no change.

--- Test results

Ok i disconnected all injectors for FD fuel lines, turned on the fuel pump. I did have a CIS pressure gauge connected, but it was in the "control" test set up (open valve to wur). No fuel came out of the fuel lines (So i presume FD is good, as I read above)

So i then connected 6 injectors, bleed them (FP running, lift AFP to max for a few seconds). Then wiped them all and watched. 5 of them were wet, 3 of them were dripping.

Now this is where i get a little puzzled. This is with the FP running. If i turn the FP off, but there is still good residual pressure, none of the injectors drip or leak, only with the FP running. Is that relevant? - i.e when car is driving, the fuel is flowing almost all of the time (except on coasting)

----- Mixture

I have read two ways of doing "basic" mixture, neither did i have a good luck with.

One way, turn mixture screw back ant clock 1 - 2 turns, then with FP running, clockwise until just flow. I got a steady dribble/drip from only a few injectors, then back off 1/2 turn. Injectors dripping

Other way, remove all lines from top of FD, with FP running, turn mixture screw clockwise until fuel rising slowly in ports, then back of 1/2 turn (anti clock) until no fuel rising in top of injector ports

strictly · 09-23-2016, 11:19 AM

P.S (See above)

Tony, can i ask what graph you use for the 045 WUR for cold control pressure? I have two porsche workshop manuals (both gen porsche) and both with different graphs from a 045. This is one of them, the other is in my garage : This one i think is from a later edition of the gen porsche manual

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by strictly

P.S (See above)

Tony, can i ask what graph you use for the 045 WUR for cold control pressure? I have two porsche workshop manuals (both gen porsche) and both with different graphs from a 045. This is one of them, the other is in my garage : This one i think is from a later edition of the gen porsche manual

Luke,

I am using the fuel control charts from the Porsche factory shop manual, Bentley, and a few other reference manuals. I have not noticed any discrepancies from these charts. I have to double check these charts when I get back home.

Tony

strictly · 08:31 AM

HI Tony,

The charts I have for the 045 are below. There is a discrepancy between the two porsche ones, i'll post them in a sec. I know how much work you do on CIS/WUR/FD, and i trust the one you use.

Before i post them a quick question about the problem i have with my 78. I posted some injector tests above, but one thing i noticed was, lets say i stopped the test, had coffee, and came back in 5 minutes, to restart the fuel pump, at that point, as soon as i reconnected the fuel pump, i would get a spray of fuel (i.e pressure surge) out of 4 of the injectors.

I understand the job of the fuel accumulator is to help prevent (or completely prevent this). It has a new fuel accumulator, fitted, i put the old one back in and same problem, but not as big a spurt.

Have you seen this before? Should i test the pressure after the fuel accumulator, but before the FD?

Charts - 045, okay here are the charts. I know its off topic, but as i need to set my WUR up anyway (for my 78, also my 75), it's as good a time as any to ask you!!

So taking a temperature, say 20C, we see the

LEFT Porsche 045 Graph = 1.5 Bar
RIGHT Porsche 045 Graph = 2.0 Bar (this is the same graph as the bentley below, but note my comment in very end paragraph)
BENTLEY (TOP) 045 Graph = 2.0 Bar

All other pressures are the same (i.e Warm, no vac = 2.7 to 3.1 Bar)

BUT

Residual is

LEFT Porsche Spec = 1.5 Bar after 20 Minutes, 1.7(!) Bar after 20 Minutes (typo?)
RIGHT Porsche Spec = 1.3 Bar after 20 Minutes, 1.1 Bar after 20 Minutes
Bentley = 1.3 after 10 minutes, and 1.1 Bar after 30 minutes

-----

I am guessing you are using the 045 Graph with 2.0 Bar Cold, at 20 Deg C (i.e same as Bentley). I think John Walker may be using the other one, as on a post about this along time ago, i remember the 1.5 Bar being discussed (around the 20C Temp)

A red herring, but i noticed on the Porsche Graph on the right it mentioned a test vacuum of 460 to 600 mBar, while we all know this is for the warm control side, why would it be mentioned ABOVE the diagram of the COLD control pressure. I'm guessing its not impossiable, the graph on the right, has been done under COLD vacuum? Hence the discrepancy between the two graphs...