Jadz928

Have you pulled the plugs and looked for fuel in the cylinders? The "feel" of vapor lock is what made me ask this question.

Do you hear injector buzzing sound with the fuel pump jumpered? I wonder is the FD metering barrel is open enough to be releasing fuel to the injectors.

Where is you AF screw set? Too far CCW will open up the FD metering barrel prematurely.

PS. Nice troubleshoot list tailpipe!

Doug_B_928

I changed the plugs last summer (this cold and hot starting issue has been happening for a long time) and they looked fine (when comparing to the images of plugs provided in Chilton's guide). I don't notice anything from the injectors when FP is jumpered, I just hear the noise coming from the FP. I don't know where my AF screw set. I have to get a long 3mm hex. I've never adjusted it. What is the range? Is it basically 360 degrees, or are there multiple turns when adjusting the screw?

I did the electrical check on the cold start this morning and it is getting power.

BTW, it would be good if you could post the info you get from Sean R regarding the specifics of using color tune, or even better start a new thread on it if you wish, as I (and I'm sure others) would be very interested to know better how it works.

Jadz928

Even if the plugs were good then, you may have fuel in the cylinders. Might be worth a looksee
IIRC, AF screw was around 30 turns from lock to lock. Might want to start a couple turn CW of center.
CCW is rich, CW is lean.

Doug_B_928

Thanks, Jim. I'll have a look at the plugs. For the AF screw, to adjust it to where you suggest do you turn it all of the way, then turn back 15 turns (half of 30 lock to lock) to get to middle, then try a couple turns CW?

Jadz928

Take out the plugs and look in the holes with a flashlight, for a pool of fuel.

Yes, 30, 15 + 2

Count the turns lock to lock, divede by 2 and add 2 CW.

jpitman2

I would count turns to end (either way, but make a note) from where it is now and document, so you can get back there. Sadly re the hot start fitting on mine (not shown in PET that I can find), my car is UK spec (C16), so I doubt it was set up for its second home - Saudi Arabia.
jp 83 Euro S AT 54k

waynestrutt

BTW, it would be good if you could post the info you get from Sean R regarding the specifics of using color tune, or even better start a new thread on it if you wish, as I (and I'm sure others) would be very interested to know better how it works.[/QUOTE]

Colortune is a replacement sparkplug where the porcelain is replaced with clear ceramic so you can see the color of the fuel as it burns in the cylinder.To properly view it you need to look down the length of the plug so you cannot use the typical wire end that our plugs now have as it will obscure your vision. They supply an extension wire to facilitate this. It was originally used on carbureted systems that had a central mixing of air and fuel in the intake runner so one plug (per carb) exchanged would tell you when you had the correct mixture.On injected systems you would need to keep moving it from plug to plug as individual injectors could possibly flow different amounts of fuel that could give different flame colors.The 928 systems aside from normal restrictions should flow equal amounts of air to each cylinder. I think colortune can help you find an injector that is flowing different from the others to swap it out or clean it and once you know they all flow the same you could trust using the colortune to adjust the mixture using just one plug exchanged. If you want to try mine your welcome to. I used it a few times on my cars that were fuelled by SU's and Webers, but after years of tuning you get used to doing them by ear so it became redundant and slower.

checkmate1996

I applaud you for taking on such an ambitious project out the gate...it took me years to understand CIS systems...

COLD START Issues - If you have a hard time cranking on COLD (e.g. overnight - start in the morning) most likely your temp sensor gauge.

Hot Start - Most likely Accumlator is leaking. I would do a physical see and smell check and the accumulator and check for leaks or any fuel smell.

Just my .02.

all the best!

checkmate1996

The "blue" book my Bosch is also excellent....

checkmate1996

If you don't mind, what were the part/brands used. I would like to copy this for my 79...

Doug_B_928

@ Jim--okay, will do the plug check. Thanks for specifics on the AF. Will get the long hex next week and give it a try.

@ JP--yeah, good idea to record starting point.

@ Wayne--that's a very kind offer. So what would be the best way to borrow yours in terms of shipping to and from?

@ checkmate--Where's the temp sensor gauge? This is a new one to add to the list.

One observation re hot start problem. The car has to be pretty hot for it to be a problem. If I run it for only half an hour it usually doesn't do it. Also, it usually only does it when it is hot outside (say 20C or more and been running for a while--more than 30 mins). Even then, I think if I turn it of and re-start it right away it is usually fine. It's when I let it sit and then try to restart (say stop the car to wash it or go in somewhere for lunch) that I need to use WOT and it sounds like it's choking/needs more air for the first 10 seconds or so. I've read some other posts in other forums which say this is usually Fuel Accumulator. There are no signs of leaks, but as I think tailpipe pointed out, it could be an internal leak from the diaphram.

checkmate1996

The temp sensor is on the front of the waterbridge tucked between the water hoses. This sensor gets our of it's proper resistance range over time causing the car to hard start when cold.

When you have the CIS pressure gauges properly hooked up, you should be able to pressurize the system. Then monitor how much bar/psi you have when fully pressured and then monitor over 15-30 minutes. According to the WSM, you should be able to maintain a range of bar/psi over that period. If it falls out of that range, you have a leak...generally either check valve or accumulator are popular starting points...

All the best...

Doug_B_928

I think I see it. Should the electrical to it be tested for power? Do you just turn on the key to the first position to send power to it or does it get power only during cranking like the cold start? Is this what is referred to as the temp II sensor? I didn't know 79 CIS had this.

Is there a way to test the accumulator, or is it just a replace it if suspected?

checkmate1996

If you are having the hard starting issue, pull the temp sensor I (II wasn't until later models) and measure the RESISTANCE using an OHM meter to verify it falls within spec. If it doesn't, prepare to spend $100 to get a new one. Chances are you getting power to it just fine, but it doesn't hurt to check. You can use a MM or electrical test light.

Also if you pull the temp sensor, prepare for fluid coming out. Not a lot, but some so have some towels handy. Also, do a search on my name and I have this all documented.

If you figure out that you aren't holding pressure there are only a few places to check for leaks:

Fuel Pump
Check valve
Fuel Fileter
Accumulator
Primary Fuel Lines coming into the engine bay (often are very old and have caused fires - tip: look on the underneath side of the hoses and flex them while looking for cracks
Injectors
Cold Start Injector

Verify all of your lines around your bosch head unit are tight and the WUR are good too.

Doug_B_928

Thank, Brad. I'm glad to hear you have a write-up on changing the temp sensor. I'll definitely search for it.

There are no visible leaks, as far as I can tell. I've replaced the check valve. I'll be doing the fuel filter and fuel lines (preventative) soon.