First start after engine install problems

[wacko]

The fuel is leaking into the cylinders when I am trying to start engine and when I lift sensor plate. I haven't had a chance to unplug the AFM as I will have to do a partial drop to access it.

With the fuel pressure gauge attached and valve closed pressure builds and holds normally but with valve open it will not build up much pressure and drops most residual pressure quickly when plate lowered. I confirmed that fuel is not leaking from drivers side injectors like I first thought when I open valve on gauge.

I am now thinking cold start injector is leaking but will have to wait until I can lower engine to gain access to it.

[boyt911sc]

Originally Posted by wacko

The fuel is leaking into the cylinders when I am trying to start engine and when I lift sensor plate. I haven't had a chance to unplug the AFM as I will have to do a partial drop to access it.

With the fuel pressure gauge attached and valve closed pressure builds and holds normally but with valve open it will not build up much pressure and drops most residual pressure quickly when plate lowered. I confirmed that fuel is not leaking from drivers side injectors like I first thought when I open valve on gauge.

I am now thinking cold start injector is leaking but will have to wait until I can lower engine to gain access to it.

It is difficult to asses what you're doing because you are giving us too many misinformation about your tests. If you want to get to the bottom of the problem try to reply or answer questions from the other posters. These are my questions:
a). With the FP running (without the motor running) are you getting fuel to the seven (7) fuel injectors (including CSV)? What's the fuel pressure reading?
b). Is the FD plunger is sitting down on the AFS arm (FP off)?

You can test the CSV in situ. No need to drop the engine just to do this simple test. Remove the CIS rubber boot on top of the throttle body to gain access to the CSV.

Try to find out the answers to these questions and people would be giving you some hints of the root cause/s. You need to test and confirm. Keep it simple.

Tony

[T77911S]

sounds like you need to stop lifting the sensor plate. that is NOT how you check fuel pressures.

you dont need to do a partial engine drop to reach the connector. if you feel you need to then remove the fuel pump relay and jumper 30 to 87a to run the pump.

the pressure will be quite low with the valve open. even down south mine would drop to .8bar cold.

to heat up the WUR plug the power into it and turn the key on. with the valve open you should see the pressure rise to around 2.8bar.

[wacko]

Tony,

Do I need to remove the CSV from the throttle body to see if it is spraying or will I be able to see it spraying installed with the boot off?

[wacko]

T77911S I tried jumping the fuel pump by running a wire from 30 to 87a but no luck. Am I doing this with fuse installed or removed? I had the fuse removed

[wacko]

Pop up valve seems good, opens and still attached 😃

Timing seems to be good as well, at least to get it started

[pors1968]

Funny post 2 and post 46 ...did not take long the guy is is gone 4 post.

[boyt911sc]

Originally Posted by VFR750

If you think you have a leaky injector, that would be a problem. The engine would run poorly at best.

Only way to confirm is pull them out. If you put each one into a jar, you'd be able to see if one leaked more than the other. You will need to lift up the metering plate to get the pump to run (with the ignition in the run position)

Obviously this is a little dangerous, as you are pumping fuel over your engine. The safer alternative is to remove them entirely, and blow compressed air through them. I have an old fuel line connected to the injector, that I use to get a bit of fuel through the injector during this bench test. At 30-40 psi nothing should flow out. At roughly 50-55 psi the injector should spray a nice fan pattern.


If you don't have a compressor, you are stuck using the fuel pump to pressurize them.

VFR750,

Where did you get this information? A good (new) CIS FI ( Bosch 0-437-502-004) is rated to operate between 36 - 52 psi. You could find these data from a factory shop manual or a Bosch CIS reference manual. For me, any fuel injector with 53 psi. or more opening pressure goes to the dumpster.

Tony

[VFR750]

My numbers were from memory.

The 36-52 range is comparable to what I said. The injectors should not flow with a low pressure applied.

I also agree, too high of a pressure is also bad.

[wacko]

Ok here are my fuel pressure test results

I will preface this that this is a Euro 1978 911sc and I do not seem to have a thermal valve installed

System pressure with valve closed and wur unplugged 5.9 Bar

Valve open with wur still unplugged pressure drops to 1.3 Bar

Plug wur in and pressure slowly rises to 3.8 Bar

I have also confirmed that none of the cylinder injectors are leaking. I assume I have to remove the CSV to check it?

I am also second guessing myself that I may have the injector lines for cylinder 2 and 3 mixed up. If anyone can post a picture or diagram of the Fuel Distributor showing which injector lines go to which cylinders that would be appreciated.

Thanks
Craig

[wacko]

I will also note that the residual pressure dropped to 0.50bar after 10 min and was at 0 after 20 min

Any advice appreicated

[boyt911sc]

Originally Posted by wacko

Ok here are my fuel pressure test results

I will preface this that this is a Euro 1978 911sc and I do not seem to have a thermal valve installed

System pressure with valve closed and wur unplugged 5.9 Bar

Valve open with wur still unplugged pressure drops to 1.3 Bar

Plug wur in and pressure slowly rises to 3.8 Bar

I have also confirmed that none of the cylinder injectors are leaking. I assume I have to remove the CSV to check it?

I am also second guessing myself that I may have the injector lines for cylinder 2 and 3 mixed up. If anyone can post a picture or diagram of the Fuel Distributor showing which injector lines go to which cylinders that would be appreciated.

Thanks
Craig

Craig,

Double check if you have a TV (thermo valve). You need one for your engine (1979) whether you have a RoW or USA MY car. Do you know what WUR do you have? The system fuel pressure is too high and out of spec.

Secondly, you need to pull out the CSV in order to see and inspect it for leak or spray pattern. Without removing it, you won't know the answers.

Lastly, the six (6) injector lines or outlets from FD are interchangeable. But assign the left side ports to cylinders 1-2-3 and the right side ports to cylinders 4-5-6. Technically, they should deliver identical amount of fuel unless something has been tinkered to affect the flow rate. Keep us posted.

Tony

[boyt911sc]

Originally Posted by wacko

I will also note that the residual pressure dropped to 0.50bar after 10 min and was at 0 after 20 min

Any advice appreicated

Craig,

Three (3) most common culprits for residual pressure loss:
1). Defective FA (fuel accumulator).
2). Defective FP check valve.
3). Defective primary pressure relief valve.

You would need a pressure gauge and the correct metric fitting to do the tests.

Tony

[wacko]

My wur has two separate numbers on it I can see without removing it 916 and 252

I have removed csv and it is not leaking. How do I check it for spray pattern?

I am pretty sure I have no thermo valve but it was running well prior with say configuration

[wacko]

I have now confirmed csv is spraying when ignition is cranked.

Not sure what to check next

[timmy2]

Outside of the CIS fuel system discussion...

Post a picture of the distributor with the cap off just as you hit TDC (Z1).
The most counterclockwise edge of the rotor should just be lined up with the mark on the distributor case with the distributor adjustment bolt in the center of the adjustment range.

I was lining my rotor up in the center of the mark when I put mine back together and it was doing what you described, I was one tooth off on the dizzy installation and couldn't get the timing to go to 5deg BTDC with the adjusting bolt range..
Just had another '78 rebuilder that contacted me about not being able to get his engine to run do exactly the same thing.

[wacko]

Here you go



This with the first of the 2 marks lined up with the mark on the fan housing

[boyt911sc]

Originally Posted by wacko

My wur has two separate numbers on it I can see without removing it 916 and 252

I have removed ctsv and it is not leaking. How do I check it for spray pattern?

I am pretty sure I have no thermo valve but it was running well prior with say configuration

Craig,

The Bosch WUR ID # is located right below the post on top of the WUR. 916 is the casting number and 252 is the serial number. Take a picture of your engine showing the intake cylinder #2 or inspect the WUR. There are two (2) hoses attached to the top of the WUR. One is the fuel line from FD and the other rubber hose goes to TV (thermo valve), in your case, goes to the DV (decel valve) since you have a missing TV (according to your post). Your WUR should be one of these 045/069/089. Which one?

If you want to get your engine to run like it should be, install the needed parts in good working condition. Otherwise, you'll be chasing your tail just get this engine to run. Believe me, there is really nothing difficult to make a CIS engine to run. Just have an open mind and listen to people with proven successes. Everything you need to know could be bench tested by DIYer like you or me. How did you verify that the CSV is not leaking? Was the FP running when you inspect the CSV?

I have not encountered a CIS engine that I could not make to run if you have the following:
Good ignition sparks and correct ignition timing
Control, system and residual fuel, pressure within spec.
No significant vacuum/air leak
FD working and correctly adjusted (good fuel injectors)

All you have to do is check and verify that the above criteria are met. Your engine should start on the first or maybe second attempt. Keep us posted.

Tony

[ossiblue]

Originally Posted by timmy2

Outside of the CIS fuel system discussion...

Post a picture of the distributor with the cap off just as you hit TDC (Z1).
The most counterclockwise edge of the rotor should just be lined up with the mark on the distributor case with the distributor adjustment bolt in the center of the adjustment range.

I was lining my rotor up in the center of the mark when I put mine back together and it was doing what you described, I was one tooth off on the dizzy installation and couldn't get the timing to go to 5deg BTDC with the adjusting bolt range..
Just had another '78 rebuilder that contacted me about not being able to get his engine to run do exactly the same thing.

I'm going to jump in here in support of Timmy2's post.

You are in very good hands with regard to the CIS issues and though some of your system is out of spec, you appear to be getting fuel delivery and given how you've done some of the tests, there certainly is enough fuel to get the engine running, if not running smoothly. Ordinarily I am of the mind to complete one area of diagnosis before moving on to another but, in this case, a quick check of the ignition would do no harm. Much of your problem is hinting at ignition rather than fuel delivery. I'd like to see you do a quick check as Timmy2 suggests and report back.

edit: just saw the pic you posted from timmy2's suggestion. Your distributor rotor looks to be centered on the mark, just like Dennis' was when his wouldn't start.

[timmy2]

Based on the photo you may be one tooth out as you look centered on the mark. Just for fun, pull the dizzy and turn it back one tooth and re-install it so the leading edge on the rotor is just to the right of the mark that lines up below it in the photo. (Could be lined up perfectly as well)
Make sure the dizzy adjustment bolt is in the center of the adjustment range when it sits like that.