78 SC Won't Start?

[scotricker]

Hi , all..

I am considering to trade my motorcycle for a very nice 78SC coupe. The owner says he has had it for many years, and occasionally it decides to not start.

It is in one of it's no start phases now, and the owner wants to sell, or in my case, trade to me.

I think this is a good deal for me, while the owner is frustrated.

He says it could be the brain box, or the start injector, or the fuel pump?

I am reasonably confident in my motorcycle mechanic abilities, so I think I will be able to easily tackle this.

The car looks well cared for, California car. with records of service.

Any advice on getting it to start?

If the seller goes for my trade, I'll just trailer it home.

[ischmitz]

Welcome to the forum. These cars are fun to work on and I am sure that you'll be able to find the issue. As you know the engine needs fuel, air and spark to run. So the first test is to check which is missing. From there it is pretty straigth forward.

The 78SC has a Bosch CIS fuel injection and a CDI ignition setup. The CDI ignition box is triggered by a hall element in the distributor. If you have no spark it could be the CDI box or the trigger wire. These are comon failures.

The fuel pump could be the issue if there is no fuel at all. Next the CIS injection works of a control pressure. There are several elements that set this pressure. If the control pressure is wrong the mixture will be off and that could cause poor running all the way to no start.

Cheers,
Ingo

[kokenm]

Every Once in a while does not tell me that there is a problem with the fuel pump.
They usually go out and stay out until you replace them. You should be able to hear it when you turn the key. If you try and start the car and it stumbles and then won't start then it could be a mixture problem and you may be flooding the engine.

There must be a hundred different reasons for the non start issues and going through each one of the three necessary parts that ischmitz pointed out is the first step. Check the easy ones first: check the fuses and the relays!
I know that I always seem to jump to the worst conclusion first and then start looking for a simple answer last. This is usually an expensive way of debugging.

if all three ( fuel, spark, air) exist then the plan for diagnosis changes.

There are huge amounts of articles on some of the most obscure solutions within this forum.. The folks around here are very good at putting their two cents in and helping to diagnose the issues. They have been a huge help to me.



So happy hunting. I would say that it is an excellent trade.

[ossiblue]

As stated by others, a no start issue is not uncommon and should be easily remedied once there is time to diagnose. However, one word of caution. I don't know the approximate value of your motorcycle, but without the engine running you are taking a gamble on the overall condition of the engine and rebuilds are not cheap. If the owner has records, of course, that will help but just keep in mind what you may be getting into.

[scotricker]

Thanks, good suggestions..
I'll post here if the trade goes through.
It's looking quite possible after some discussions today.
!!

[T77911S]

the 78 is a good car. it has the large port heads on it. if you decide not to get it, post it here. someone else may want it.

sounds like the car has been sitting. the first thing i would do is check for a stuck plunger in the fuel distributor. this also checks for fuel pressure and that fuel is getting to the engine.
the plunger could give you sometimes start and sometimes not.

if it were me, i would buy it with the intent of putting on a new warmup regulator, new injectors, pulling the CIS and replacing ALL the rubber seals and hoses that go on the CIS.

[scotricker]

OK, trade completed. !
Trailered the car home yesterday.

the CDI box makes a high pitched sound, so does that mean it's alive?
the previous owner had the wire replaced from the CDI to the distributor.
I am not sure if I hear the fuel pump or not?

Tha car turns over and sounds like it wants to start, with a few encouraging putts
but just doesn't catch.

Can I test the fuel pump relay out of the car?
Should I just get a new CDI and coil? The one that's in there is Bosch and looks like it's been in there for awhile.

Is it spark, or is it gas? How to decide?

Any help? thanks

[ischmitz]

If the CDI box makes a high-pitched noise it is not a guarantee for it to be alive. It could still have a bad trigger input. Take one spark plug connector off and use an old spark plug grounded to some engine metal part to check while an assistant is cranking. If you see sparks you know the box works and the triggering works as well.

Ingo

[scotricker]

good idea, that sounds easy to test. I don't think I have any old spark plugs laying around though. I guess I could go buy one to use for a tester.
What should I go get?

[longhornchris04]

One potentially hazardous way to check fuel is to:

1 - get six clear, fuel safe containers - bonus mark even measurement lines.
2 - remove your fuel injectors and place into said containers - this may be tricky to get them balanced.
3 - set ignition to run (not start!!!) - best done by assistant while you hang out with a fire extinguisher in back
4 - gently lift the fuel distributor sensor plate - fuel should flow pretty much immediatly
5 - observe fuel squirt into containers
6 - measure fuel, you should have equal distribution. If not your injectors or fuel distributor are bad.

Have an assistant on hand w/ a fire extinguisher or two just in case. Also so be careful.

If wired correctly, the fuel pump shouldn't activate until you lift the sensor plate, there's a safety switch to kill the fuel pump should the engine stall. If you have additional assistance someone can listen for the fuel pump to activate when you lift the plate.

It is also possible to go injector by injector, but this does mean the others will be dumping fuel into the intake manifold and will cause problems the next time you try to start.

This test, of course, only tells you that the fuel system is distributing fuel evenly. It won't tell you that your mixture is too rich/lean for the engine to start. It obviously won't eliminate the anything spark related.

[scotricker]

that scares me!

[longhornchris04]

Hey, I said it was potentially hazardous.

The good news is that CIS injectors aren't "that" high pressure so if you tape them into the jars they won't go anywhere. Plus, the moment you let go of the sensor plate they should stop (if they don't you have other problems).

Now's as good a time as any, do you have the Bently Guide for 911 SC's? If not, then get it. That procedure is (granted by memory) from their section about testing the fuel distributor.

If you are careful it shouldn't be a problem.

Regardless, I'd follow T77911S' advice and put new "stuff" on it and get your pressures checked. At least the seals, hoses, and injectors. The WUR for a 78/79 is expensive (~$1000 from our host), only replace if necessary and consider the UTCIS-V (~$500 from host) which is a programmable replacement regulator... unless you are in California in which case you are SOL (not CARB approved).

[scotricker]

I got a lame haynes 911 manual that is not specific for sc.
I do not know of the Bently guide. where should I get that one?

[longhornchris04]

Pelican carries it, as does Amazon.com. Its $100, but worth it.

[scotricker]

I will get the book,
but what should I go out there and check on until my book gets here?

[boyt911sc]

Originally Posted by scotricker

Hi , all..

I am considering to trade my motorcycle for a very nice 78SC coupe. The owner says he has had it for many years, and occasionally it decides to not start.

It is in one of it's no start phases now, and the owner wants to sell, or in my case, trade to me.

I think this is a good deal for me, while the owner is frustrated.

He says it could be the brain box, or the start injector, or the fuel pump?

I am reasonably confident in my motorcycle mechanic abilities, so I think I will be able to easily tackle this.

The car looks well cared for, California car. with records of service.

Any advice on getting it to start?

If the seller goes for my trade, I'll just trailer it home.

Scotricker,

Haynes manual will be helpful but not as good reference like Bentley SC manual. But foremost of all, you need a fuel injection fuel pressure gauge kit to do a meaningful and effective CIS troubleshooting. Otherwise, you'll be doing a lot of quess works in your quest to make the car run.

If the car was well maintained before, you should be able to make this car run at minimal expenditure. You don't have to be an experienced CIS troubleshooter to make this car run again. With all the guys in this forum, I've never found a problem these folks could not diagnose correctly.

The key is giving us the correct information and feedback to what's happening in your work. Your problem is not unique. It is a common problem and has been tackled many times before. Good luck and keep us posted.

Tony

[scotricker]

Thanks for your comment.
Is the fuel injection pressure kit something I buy at the local autoparts store? Or from Pelican? Or rent one?

[Paulporsche]

JC Whitney sells them for about $60. That is, when they actually have them. BTW make sure you get the one for CIS.

I don't see where you are located, but maybe some local kind hearted Pelican can loan you one. A fellow Torontonian did that for me recently when my gauge was backordered by JCW, and it was a great help.

[T77911S]

Originally Posted by longhornchris04

One potentially hazardous way to check fuel is to:

1 - get six clear, fuel safe containers - bonus mark even measurement lines.
2 - remove your fuel injectors and place into said containers - this may be tricky to get them balanced.
3 - set ignition to run (not start!!!) - best done by assistant while you hang out with a fire extinguisher in back
4 - gently lift the fuel distributor sensor plate - fuel should flow pretty much immediatly
5 - observe fuel squirt into containers
6 - measure fuel, you should have equal distribution. If not your injectors or fuel distributor are bad.

Have an assistant on hand w/ a fire extinguisher or two just in case. Also so be careful.

If wired correctly, the fuel pump shouldn't activate until you lift the sensor plate, there's a safety switch to kill the fuel pump should the engine stall. If you have additional assistance someone can listen for the fuel pump to activate when you lift the plate.

It is also possible to go injector by injector, but this does mean the others will be dumping fuel into the intake manifold and will cause problems the next time you try to start.

This test, of course, only tells you that the fuel system is distributing fuel evenly. It won't tell you that your mixture is too rich/lean for the engine to start. It obviously won't eliminate the anything spark related.

this is a good test. i found a bad injector line on mine. i weighed the fuel on a postal scale though. its not that dangerous to do, a little involved just to check for fuel delivery for a no start. you can pull one injector to do a quik test. although you may want to do this down the road to check patterns too. this will also check that the plunger is not stuck. if there is ANY play when you lift the plate until you feel resistance, the plunger is stuck. make sure you can raise the plate all the way up.
this is common on cars that sit.
i have a spare head, even though the plunger is not corroded, it is hard to get it out.

[scotricker]

the plug wires are installed wrong.

Can someone help me with a picture of where each wire goes?

I believe that I read somewhere that the distributor turns counterclockwise,

And I got the firing order as 1 6 2 4 3 5

but which cylinders are which number?

and how do I be sure where #1 is on the dist?