Hard Starting SC

[brianhiggi]

I have a '78 SC with a starting problem.
When I try to start the car it starts but only for a few seconds then dies out and won't start again. If I advance the timing by turning the distributor I can get it to start but even then I've got to give it gas until it heats up or it will die too.

I had the mixture adjusted in October the same day the weather got cold. I don't know if it is because of either of those 2 factors.
Is it the WUR, Intake vacuum leak or spark plugs? The 4 month old plugs look a little ashy white.

[Bob Kontak]

How did it run in October after the adjustment was made? Why was it adjusted. How did it run before?

My first guess (assumption) is that it is too lean - given your data on the adjustment and assuming it has been this way since Oct. The cold start valve helps it start then is shut off when you let go of the key. The injectors may not be delivering enough fuel because cold control pressure is not low enough.

You can check for fuel flow at the injectors but you won't know the pressures re the WUR concern without gauges. Many folks mention the fuel filter as a culprit if there is fuel delivery problems. Do you know the air sensor lifting trick?

Air leak may be a possibility but it is also a possibility with almost every poor operating condition with CIS.

[T77911S]

check for air leaks and put gauges on and check control pressures.

[boyt911sc]

Originally Posted by T77911S

check for air leaks and put gauges on and check control pressures.

The above suggestion is what I would strongly suggest before doing any further work. Plus tinkering the mixture screw setting without verifying the absence of air leak/s would complicate your problem. The early CIS engines (non-lambda) are very simple to maintain.

Tony

[Joe Bob]

Fuel pressure and air leaks on CIS......futzing with timing and mix will cause a lean condition and burn a valve.

[Bob Kontak]

Originally Posted by T77911S

check for air leaks and put gauges on and check control pressures.

+1

This is your starting point if you have the tools. If you do not have the tools and you do not respond to queries (e.g., how long has this problem been occurring?) then it is guess work for those trying to help you. There are several examples of threads over 100 posts where the culprit was something as simple as a crack in the airbox.

We need your feedback.

[T77911S]

if you dont have the tools, you can check the inlet to the WUR for now, the screen can get dirty and raise the FP, but that will also effect warm running too.

[brianhiggi]

How did it
Thanks everyone for the replies.
Here's a little more info that might help.
I bought the car a year ago with no history and it had sat for a few years before I got it started. Before the adjustment the car started and ran pretty good except when the engine would warm-up the idle would surge. After the adjustment it still has a surging idle but is hard to start. The shop I took the car to did a smoke test to see if there was a vacuum leak said they didn't find a leak but I suspect there is one. Would a vacuum leak cause the car to have difficulty starting that it wouldn't have during warm weather days?
Also what causes low cold fuel pressure?
I'm somewhat familiar with the air sensor lifting trick. I'll look up a thread about it and try it.
The screen on the inlet to the wur looks good.
I replaced the fuel filter last summer before starting it for the first time but the gas tank had a few flecks of rust in it. Could that clog up the filter?

[boyt911sc]

Originally Posted by brianhiggi

How did it
Thanks everyone for the replies.
Here's a little more info that might help.
I bought the car a year ago with no history and it had sat for a few years before I got it started. Before the adjustment the car started and ran pretty good except when the engine would warm-up the idle would surge. After the adjustment it still has a surging idle but is hard to start. The shop I took the car to did a smoke test to see if there was a vacuum leak said they didn't find a leak but I suspect there is one. Would a vacuum leak cause the car to have difficulty starting that it wouldn't have during warm weather days?
Also what causes low cold fuel pressure?
I'm somewhat familiar with the air sensor lifting trick. I'll look up a thread about it and try it.
The screen on the inlet to the wur looks good.
I replaced the fuel filter last summer before starting it for the first time but the gas tank had a few flecks of rust in it. Could that clog up the filter?

Brian,

Hook up a fuel injection pressure gauge and you'll be able to check the following without even running the engine.
a). Fuel pressures (system, control, and residual).
b). FP delivery capacity & check valve.
c). WUR (cold & warm control fuel pressures).
d). Fuel injectors (spray pattern & leak test).
e). CSV (spray pattern & leak test).
f). FA (fuel accumulator).
g). Fuel distributor & check valve.
h). Fuel filter.

These are just some of the things that come on top my head that you could check yourself without running the engine per se. It is mandatory to have a pressure gauge kit when troubleshooting a fuel injection system. And if you don't use one, I'll say good luck and hope you get lucky. Keep us posted.

Tony

[brianhiggi]

I did a little tinkering over the weekend. I am a newbie so basic things take me a while.
I did the air sensor lifting trick and it began squealing, I then tried starting the car and nothing. It definitely smelled like gas after trying to start. I pulled the fuel injectors and they were wet. The tempeture outside was quite warm at 60 degrees so it's not the cold weather keeping the car from starting properly, but last summer it started pretty well.
The car seems to be getting harder and harder to start. Is the mixture causing the plugs to foul?

[T77911S]

yes.

you HAVE to get some gauges and check pressures.

one other thing is to ccheck for is voltage at the WUR.

what you have described is a typical bad WUR (or no voltage) at the WUR. someone has compensated for the hbad running when warm but created a cold start problem.
this is the result of turning srews before checking pressures. that is still better than spending $$$ before checking pressures.

[brianhiggi]

I'm gonna check the voltage to the WUR the second I get home from work.
I have one of those yellow voltage reader things but I don't know how to work it. How exactly do I use it to test the WUR volts and how many should I be looking for. Where do I turn the knob on the voltage meter?

[Bob Kontak]

Get yourself a normal house hold battery - e.g., for a flashlight. Put the pointer on DCV - 20. Read the voltage on the battery and touch the probes to the battery ends. New battery will give a bit more than rated. Now you are ready to go.

Touch the leads to the WUR contacts with the key in the on position. Should be around 12V.

[1982911SCTarga]

Bob, if the original poster's car is correctly wired, he needs to jumper the fuel pump relay (pins 30 and 87a) to be able to have current flowing to the WUR, or control pressure regulator, with the key in the "on" position and the engine not running. Otherwise, he will get a false negative on WUR voltage.

Just trying to be accurate.

Brian

[brianhiggi]

Thanks Bob. I checked the volts on the WUR contacts and it read 10.25. Is that close enough to 12 to be normal? I also checked the OHMs on the WUR and it was about 30.
Is there any other way to check the WUR to see if it is operating correctly? Should I look for a new (used) WUR?

[boyt911sc]

Originally Posted by brianhiggi

Thanks Bob. I checked the volts on the WUR contacts and it read 10.25. Is that close enough to 12 to be normal? I also checked the OHMs on the WUR and it was about 30.
Is there any other way to check the WUR to see if it is operating correctly? Should I look for a new (used) WUR?

Brian,

If you want to know if your WUR is working, attach a fuel pressure gauge and run the FP. Record the cold control pressure versus time (up to 4 or 5 minutes) until the warm control pressure stabilizes. This will be the WUR profile. You don't need to run the engine, just the FP with the ignition switch @ ON position.

Some of my WUR collection:




Suggestion: Do not replace CIS component/s unless verified to be defective. Tests will confirm its condition. PM me and I'll test (free) it for you.

Tony

[brianhiggi]

Would a fuel pump that is on it's way out cause any of the symptoms we've talked about? Like hard starting, surging idle, or low fuel pressure?
My fuel pump is a little loud and occasionally it makes a clanking sound when I turn the starter on and off and on again.

[T77911S]

my FP is loud too.

check the fuel pressures. you will also check the system fuel pressure.

[brianhiggi]

Sounds like I need to check the fuel pressures.
Tony has offered to check my WUR for free. After that I'll figure out how to test the pressures. Any good threads on checking fuel pressures for dummies?

[Bob Kontak]

Originally Posted by 1982911SCTarga

Bob, if the original poster's car is correctly wired, he needs to jumper the fuel pump relay (pins 30 and 87a) to be able to have current flowing to the WUR, or control pressure regulator, with the key in the "on" position and the engine not running. Otherwise, he will get a false negative on WUR voltage.

Just trying to be accurate.

Brian

Brian. Thanks. You are absolutely correct. Thanks for pointing this out. I always learn the best when I get egg on my face. Thanks for being kind.

Edit - A point worth clarifying is the FP is jumped by jumping the 87a and 30 HOLES IN THE RELAY SOCKET with a wire - the pin holes - not the pins on the relay. Not an issue to the experienced but for a learner (like me) it can be misinterpreted. Connecting the pins and plugging it in will spin the starter. The factory manual points out to use a "spare" relay (with pins jumpered - not holes) which will spin the starter if the relay is good. Last year we discussed the Porsche translation of "spare" relay to english is intended to mean non-functioning relay.