Will not start...

g rad · 10-19-2008, 07:40 AM

I have about a 1 K on my rebuilt 2.7 76s,, while driving home from work, it just died, after checking connections around electrical connections on engine. I had a loud exaust backfire and it started. Drove a few more miles and same again, a block away from home was the final failure and no start....

Towed it home,, I have spark at the plugs,, the fuel pump is running when it is supposed to... The engine fires up for a half second but no more sign of life...I'm running out of things to look for... any help to get me to work Monday would be appreciated....

g rad · 10-19-2008, 08:30 AM

Just installed a new rotor and cap to distributor, the new points are at .011 and still I have the same, wants to run, fires for half a second, then nothing.... I'm grabbing at straws,,, will pull cis injectors and look at flows next.... coil??? desperate, George

Formerly Steve Wilkinson · 10-19-2008, 09:11 AM

I had a very similar problem on my '83 SC recently. Driving along, the car would suddenly die for anywhere from half a second to a few seconds, then pick up again. Funny thing was, all the instruments died too, then came back to life. The advice I got was to replace the electrical cassette on the rear of the ignition lock (i.e. toward the front of the car). It's a bear to get at, but I did it and it has run fine ever since, though that probably means a total of 300 miles, since I rarely drive it.

CliffBrown · 10-19-2008, 10:50 AM

Quote:

Originally Posted by g rad

The engine fires up for a half second but no more sign of life.

George

If I were to guess, I would think fuel is the problem. You state that it starts for half a second, tells me the ignition system is working.

Sounds like the motor is starting using the cold start fuel but stops after the fuel is cut-off after you release the key in the start position.

Do a quick check of the injectors by jumping the fuel pump and lifting the sensor plate. You should be able to hear the injectors sing. Don't mistake the sound of the CDI.

Do not let the injectors flow very long and do not try to crank the motor for several minutes after allowing the injectors to pump unburned fuel. Hydraulic lock and damage can result.

Baz · Baz's Garage

Cliff,
Do the injectors make a ZZZZZZZZZ sound when the air flow sensor plate is lifted?
I just went through this in troubleshooting a no-start scenario. I suspect my fuel pump may be gone. I didn't hear anything from it when the plate was lifted - just a loud buzzing sound (ZZZZZZZZ).
Thanks,

CliffBrown · 10-19-2008, 01:20 PM

Quote:

Originally Posted by Baz

Cliff,
Do the injectors make a ZZZZZZZZZ sound when the air flow sensor plate is lifted?
I just went through this in troubleshooting a no-start scenario. I suspect my fuel pump may be gone. I didn't hear anything from it when the plate was lifted - just a loud buzzing sound (ZZZZZZZZ).
Thanks,

With the key in the on position the CDI box should be making a buzz sound, put your hand on the CDI to determine if that's the ZZZ sound you're hearing.

The injectors shouldn't be flowing unless the sensor plate is lifted.

Baz · Baz's Garage

Ignition on.
The CD Box is humming.
Then...after I lift the air flow sensor plate, I hear an additional sound....a higher pitched electrical-like sound. hard to describe. I don't know what the injectors are supposed to sound like. Is it a high pitch sound?
Thanks Cliff!

CliffBrown · 10-19-2008, 01:29 PM

Quote:

Originally Posted by Baz

Ignition on.
The CD Box is humming.
Then...after I lift the air flow sensor plate, I hear an additional sound....a higher pitched electrical-like sound. hard to describe. I don't know what the injectors are supposed to sound like. Is it a high pitch sound?
Thanks Cliff!

Sounds right.

Baz · Baz's Garage

Quote:

Originally Posted by CliffBrown

Sounds right.

Thanks Cliff - must be a fuel pump issue. I will investigate tomorow. I have a used spare one I can install if needed.
Thanks again for your input!

CliffBrown · 10-19-2008, 01:36 PM

Quote:

Originally Posted by Baz

Thanks Cliff - must be a fuel pump issue. I will investigate tomorow. I have a used spare one I can install if needed.
Thanks again for your input!

If the injectors are flowing then the fuel pump is working.

Baz · Baz's Garage

Quote:

Originally Posted by CliffBrown

If the injectors are flowing then the fuel pump is working.

That's true but......the "buzzing" sound, sounded more electrical than like fuel flowing. Another Pelican said it sounded like the Frequency Valve.

I'm jacking her up tomorrow and popping the skid plate and then I'll know for sure.

Will let you know what happens.....thanks again!

CliffBrown · 10-19-2008, 05:39 PM

Quote:

Originally Posted by Baz

That's true but......the "buzzing" sound, sounded more electrical than like fuel flowing. Another Pelican said it sounded like the Frequency Valve.

I don't know the year of your car but the Freq. valve is only used on the later SC, after '81 I think.

Baz · Baz's Garage

Quote:

Originally Posted by CliffBrown

I don't know the year of your car but the Freq. valve is only used on the later SC, after '81 I think.

That makes sense.....it's an '83.

I didn't recognize the sound because my previous SC was an '81. Live and learn....

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Baz

That makes sense.....it's an '83.

I didn't recognize the sound because my previous SC was an '81. Live and learn....

Bazza,

Just to clarify some basic facts, my understanding is that all late SC's ('80-'83) have frequency valve in their fuel delivery system. One distinct difference between the '80 and '81-'83's wiring diagrams are the additional temperature switch (35°C) and microswitch (15°C) for the latter group.

Would somebody knowledgeable about this subject make a comment? Thanks.

Tony

stlrj · 07:16 AM

Stop wasting your time with complicated diagnostics. You simply have a blown air box. ( that's what that boom was all about, an intake explosion, not an exhaust backfire)

Ask me how I know.

End of discussion.

Paulporsche · 10-20-2008, 07:44 AM

Do you have an airbox popoff valve installed? If so, did you check it? If not, If not, better check the airbox per stlrj. See if there are any loose screws on the inside.

Baz · Baz's Garage

Quote:

Originally Posted by boyt911sc

Bazza,

Just to clarify some basic facts, my understanding is that all late SC's ('80-'83) have frequency valve in their fuel delivery system. One distinct difference between the '80 and '81-'83's wiring diagrams are the additional temperature switch (35°C) and microswitch (15°C) for the latter group.

Would somebody knowledgeable about this subject make a comment? Thanks.

Tony

Hi Tony,

You are correct, here is a great website which charts the CIS components through the years:
http://members.rennlist.com/jimwms/CIS/CIShome.html

BTW, it WAS the frequency valve making that buzzing sound and it WAS the fuel pump causing my no-start. I tapped it a couple times and it started running! Could have gotten clogged up a bit from siting so long.

Cheers,

PS - Sorry to hijack your thread, George!

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by g rad

I have about a 1 K on my rebuilt 2.7 76s,, while driving home from work, it just died, after checking connections around electrical connections on engine. I had a loud exaust backfire and it started. Drove a few more miles and same again, a block away from home was the final failure and no start....

Towed it home,, I have spark at the plugs,, the fuel pump is running when it is supposed to... The engine fires up for a half second but no more sign of life...I'm running out of things to look for... any help to get me to work Monday would be appreciated....

G Rad,

Do you have a CIS fuel pressure gauge kit? Using one to troubleshoot your problem eliminates the quessing game and will save you time and money. For as little as $65, you could buy a decent kit and the savings will be enough to pay for itself after using it for a few times.

The first thing I usually do when doing a CIS troubleshooting is hook up this gauge. CIS is all about fuel pressure delivery and vacuum. The fuel pump maybe running, but if the delivery pressure is below spec, this will cause some running problem. Have a significant air leak, it will never run at all.

Replacing parts without verifying if it is defective is very costly unless you want to have spares for every CIS components. You could have bought a new air box and still have the same nagging problem. So being able to do simple diagnostic test is important in maintaining your CIS running good. Good luck.

Tony

stlrj · 10-21-2008, 08:18 AM

Quote:

Originally Posted by g rad

The engine fires up for a half second but no more sign of life..

The reason it fires up initially is because the cold start valve sprays just enough gas to get it started but it will never stay running with the huge vacuum leak that your broken air box has created.

g rad · 10-21-2008, 08:33 AM

After poking around in the front fuse box, I found the top red wire to the first fuse (right side of box) just laying on the set screw,, from the factory it only caught the very end of the hard stiff,30+ year old, red wire.... Pushed it in farther and tightened it up... all was well... Also found the O ring in my popoff valve was out of it's groove causing the lean backfire.... I made it to work the next day,,, thanks all, g rad