Crank but no Fire

[nyum96]

I've spent a month researching and testing and retesting every electrical connection. One day she runs, the next day nothing but cranking. There is gas in the lines. The injectors are new and are opening and closing when cranking. There are only 3 "old " components left on the car from the PO, the dizzy, battery, and starter.

When it ran, I replaced the ignition switch. Worked and ran until it didnt start 5 days later.I read all the tech articles. Tested the coil, had power (12v) but no spark from secondary so I installed a new coil, which was also "old." Still at square one.

Now the battery is dead. Even tried jump-starting. No go. The only "strange" thing is that the day before this mess, the "seatbelt" light was bright then went dim. I research and checked the wires, nothing. Took apart the dash, nothing. Replaced all wires from battery to starter, nothing. New sparkplug wires, nothing. New distributor and rotor, nothing. Have compufire, bought 2 more units , nothing. Just for kicks, I replaced the accelorator cable in 30 minute, nothing. Now, my brain hurts and I've replaced, sanded, and tightened all grounds ie: engine, battery, transmission, etc.

The following are my questions:

1: Will a bad battery cause just cranking? Crank but no fire

2: will a bad starter solenoid cause just cranking or would it not crank at all?

3: Will the dim "seatbelt" light interfere with it not starting?

4: Would a bad starter gear on the flywheel cause it to crank and not fire?

5: Anyone else have a simular problem?

6: Should I wait a little long and hope it starts as the summer goes by?

Thanks a ton!

[Pritchard]

The seatbelt relay is located under the passenger's seat. It can cause the car not to start. Others will chime in and tell you how to bypass this relay. Mine was done by PO. I have a 2.0 and I guess it works the same on all 914's.

Good Luck!

Pritchard

[Dave at Pelican Parts]

That's on the 74s and some 75s. The relay will keep the starter from cranking. It sounds like the starter cranks fine, here.

Answers to the original questions:
A battery that has very very little internal resistance can be discharged far enough that it doesn't have enough voltage to operate the electronics, but it will still be able to put out enough current to crank the starter. Happened to a buddy's long-term-storage 911 with an Optima in it. Very unlikely, though. Check battery voltage (a real voltmeter across the battery terminals, not the center console one) while cranking and make sure that it is at least 9V.

The other answers are all, "In general, no."


You need three things to run. Fuel, spark, and air (or compression).

Check for spark. Tape a spare plug to a ground like the fan shroud. Plug in a plug wire. Have someone crank the engine, and look for sparks at the plug.

Check for fuel. Put the injectors into glass jars. Have someone crank the starter and look for fuel. Bonus--you get to see the spray pattern as well.

Check for compression. Hook up a compression tester and see what compression readings your engine has.

If your car still won't run, all that's left is (spark) timing, and the amount of fuel going in.

--DD

[nyum96]

Thanks to all!

The compression ranges from 125-130 on all 4 cylinders.

All new bosch fuel injectors, fuel coming out.

New bosch fuel pump, still ticking.

I think my problem is spark. I hear the injectors open and close while cranking. I just can't get the secondary to spark. I grounded the negative wire from the tach and measured current. It was around 11.5v. I even measured the voltage while trying to jump start. That reading was around 13.5 volts at the coil. I tried the secondary wire from the coil and grounded it on the shroud. Still no spark. The only thing I haven't check in a while is the fuel pressure. It was set at 30psi for the hot summers down here. That was done 2 months ago.

I have compression, I have fuel, but no spark. I may go ahead and get a new battery because the one I have is 4 years old. Just another problem down the road waiting to happen. This is so simple that I know I'm looking right at the problem and its looking back at me laughing! CHT replaced 2 weeks ago. Just for kicks, I burned up my compufire just to make sure I was getting power to that.


Another last question, Would the FI brains be malfunctioning?

Thanks again for your answers. I'll fly you down to GA if you want. I'll try rechecking all conections and grounds again tonight.

Barry B

[Dave at Pelican Parts]

They can malfunction, but that won't cause a lack of spark.

OK, so you have verified that you have +12V on the coil (+) terminal when the key is on.

Unplug the tach wire from the coil (-) terminal, and also the green points wire. Tape your center coil wire about 1/4" away from the fan shroud, and plug in a spare length of wire to the coil (-) terminal.

Turn the key on. Touch the spare wire to the battery ground post and then pull it away again. You should get a spark on one of those two occasions. If not, your coil is bad--period.

If the coil checks out, then turn the key off again. Rotate the motor so that the points are closed. Unplug the points from the condensor--there's a plug going through the side of the distributor body for that. Check continuity between that connector and the engine case when the points are closed. Use a screwdriver to open the points, make sure that you don't get connectivity. (Visually inspect the ground braid between the points plate and the distributor body as well.)

If that checks, your points are working. Hook them back up again and hook the green wire to the coil (-) terminal. Turn the key back on. Use the screwdriver to open the points and let the spring snap them closed again. During the open or the close, you should get a spark at the coil wire.

If not, then the condensor has crapped out on you.

If you get a spark out of the coil, then your problem is in the upper part of the distributor--the cap, rotor, or plug wires.

--DD

[hardflex]

sounds like no spark here too. if you've tried everything else,why don't you put in points/condensor to troubleshoot the spark problem. It has to be from either distibutor based or coil based.

point to note- a helper hooked up the hot wire that's supposed to go to coil positive accidentally to coil negative, and fried my pertronix in short order. luckily i had a spare. I guess a dwell meter would measure pulses from a compufire, which might be a way to verify if it was working properly.

spark is spark, it will come when summoned properly.

[Tidybuoy]

I had a similar problem. For some reason, the car would just not start.

It turned out to be the Fuel Pump Relay & possibly the fuel pump (I replaced both).

I first replaced the fuel pump & it seemed that the problem was cured until about 3 months later it did the same thing (cranks but no start).

When looking over the fuel pump relay, it turned out to be full of rust dust. A good cleaning & the car started right up - I have since replaced with a new relay & I have not had a problem in a year.

Vern

[Kevin Powers]

i spent atleast 2 days with no start due to a bad compfire, new right from the box. if you have continuity from the - side of the coil to ground then my guess the problem is a connection between the coil and the dist. spade connections can go sideways with no appearent damage. the green condensor wire goes to the - side of the coil. today i start the ordeal of trying to return the defective compfire. wish me luck.

kevin

[nyum96]

I now have spark, or at least a tiny blue spark comes out of the wire from the coil to the dist. I guess I was expecting a massive spark but after paying closer attention, I found it. So now my focus is on the dist. I am going to take the compufire out (no problems in 3 year) and put point back in. Thanks a lot. for the help. I have cleaner and conditioned all the fuses and fuse panels. I also had the fuel pump problem a year ago. Thanks for your replys.

[nyum96]

Figured it out! After a lot of blood, sweat, and endless nights, it turned out to be the mechanical portion of the ignition switch. When the key was in the cylinder and turned, it wasnt making contact all the way which caused the intermediate starting problems. Thanks for all y'aws help.

bb