1972 911T roadside assistance questions

[vick]

Original 2.4L & MFI. Just did a 500 mile leg running healthy and strong the whole way and literally as I was pulling into a hotel parking lot the engine gave a short backfire from idle and quit, won’t restart.

The fuel pump is working with the key on and the starter cranks the engine just fine. Tries to start, stumbles for a minute and quits. Sounds like no fuel.

Easy troubleshooting steps before I begin exploring repair resources in the depths of Mississippi and/or just find a uhaul rig to load it up?

Many thanks in advance

[jpnovak]

Do you have timing light? check spark. Could be failing CDI.

Is MFI pump belt still in place? Assume so if engine sputters.

pull sender and check for clean fuel tank. Possible fuel filter sock clogged and no fuel flow.

Pull fuel supply line after engine filter to MFI pump and check flow into catch bottle. This will verify fuel pump still working. Fuel pump should be always on with key. If you can, check flow into engine bay filter and out of filter into injection pump. This will isolate clogged filter.

Where in MS? We might be able to help located help closer than home or your destination.

[Jeff Higgins]

Still running points? If so, I bet they are not opening. Or too pitted to work. Both are common problems with the very low quality points available today.

[bahman]

Originally Posted by Jeff Higgins

Still running points? If so, I bet they are not opening. Or too pitted to work. Both are common problems with the very low quality points available today.

+1
Exact problem happened with my ‘72E. Culprit: Closed points, which also damaged CDI box.

[spyerx]

Air, spark, fuel

Verify each

My bet is ignition. Coil, cdi, points.

My 914 6 did exactly this it was a coil that just died.

[smadsen]

Check the airbox (remove the air filter). If you have the aftermarket pop off gizmo, it may have broken loose from the hole causing a massive air leak. Use duct tape over the hole until you can effect a more permanent fix. Or glue the pop off gizmo back in the hole with JB Weld, that's prolly the way it was installed (and caused the problem). Car won't start unless you plug the hole with something.

[HarryD]

Originally Posted by smadsen

Check the airbox (remove the air filter). If you have the aftermarket pop off gizmo, it may have broken loose from the hole causing a massive air leak. Use duct tape over the hole until you can effect a more permanent fix. Or glue the pop off gizmo back in the hole with JB Weld, that's prolly the way it was installed (and caused the problem). Car won't start unless you plug the hole with something.

OP has a 72 which is pre CIS. No pop off valve.

He needs to verify the basics. Fuel, air, spark.

Fuel verification has been discussed above.

Check your points to be sure they are opening and closing.

Lots of threads on this topic. Here’s one:
How do i check a coil with a timing light??

To get a spark to the spark plug in the engine. Several things need to happen. First, you need power to the CDI. Next you need to have a way to trigger the CDI (the points do this by opening and closing). Then the CDI will then send a pulse to the coil which will increause the voltage and send it through the high tension lead to the rotor and to the selected spark plug. You need to verify that each step in this chain is working.

1) Verify that the CDI is getting power.

2) Verify that the CDI is producing power to make a spark. You can do this with a "telegraph" test. Take the high tension lead off of the center of the distributor and put a spark plug on it. Ground the threaded part. With your plug attached to the center lead, open the distributor, remove the rotor, place your key in the run position, and manually open and close the points. Each time you cycle, you should see a spark from the plug. If you do not, you may have a bad CDI. Or Coil.

3) Verify that the coil gets a signal when you crank. Replace the rotor and distributor cap. Leave the plug on the center high tension lead. Crank the engine. Do you see a spark? If so, you are getting spark to the distributor. If not, your point gap may be off or there is some other problem with the connections.

4) Verify that the spark goes to the spark plug wires. Reattach the center lead to the distributor. Attach you spark plug to one of the leads going to the cylinder spark plugs and ground. Crank engine. If you see a spark you may have a timing problem. If no spark, you have a problem with your rotor or distributor cap or your wires are improperly seated.

Do a search here as there are many threads on this topic. Look especially for the ones by early_s_man. Warren (RIP) left a great deal of knowledge on troubleshooting this problem.

[faapgar]

When you crank it over this morning see if the tach bounces or moves at all.Take a clean match book and slide it between the points.You might see a spot of oil film.Any questions call me at 910-420-8285.Fred

[vick]

Thanks all for the troubleshooting points and support! Was wiped out from a long day last night and was happy to end things with the car safely in a parking spot. Headed out now to start fresh.

Couple of notes from the cars records - within the last 1000 miles it had some work done to address poor idling. Surprising considering how well it ran all day yesterday. Had points replaced, fuel pressure was checked, fuel tank inspected for debris, and mechanical fuel injection pump was resealed. No indication coil or CDI was checked out.

[icarp]

Points replaced could mean fresh lube on the distributor cam , too much lube can fly off and hit the contact of the points . Make sure the points are super clean . Even some Biz cards can leave a residue that will compromise the points . As Fred said a match book folded backwards , non printed side to the points , slide that through 5 times?, It might help
Ian

[vick]

Quick update - looked everything over and nothing seemed out of place. Cranked it to give it a shot and it started right up. Let it idle and shut down again to try restart - started a little hard but caught and found a good idle.

After shutdown I did open the distributor to check the points. Seemed good but ran a piece of thin cardboard through for good measure - no contaminants noted.

Going to give it a shot and press north. Objective is Boston, anyone want to place odds?

[spyerx]

Coil or cdi is my bet. Heat induced.

[vick]

And another update...made it a few blocks from the hotel and quit again, same story. Off to grab a uhaul and get it loaded

[john70t]

Sounds like something heating up or a inconsistent fuel blockage. Not a setting.

Once an 82 VW Golf ran fine with only few random shutoffs while running. Then it wouldn't restart after being parked. Had to wait an hour before it would start again. I took the Bosche fuel pump relay cover off and it was visibly burnt inside. Maybe too much draw from the pump.

[kltarga72]

My 72 T would do the same thing. It would stop running with no warning, let it set 60 minutes or so and would start up and run with no issues. A few days later it would do the same thing, it was the CDI, when it heats up it fails.
On my 72 S the stone type factory fuel filter on the gas tank was old and clogged and would starve the engine of fuel but the indication was it would run rough until you ran the engine at a lower rpm. Filter would not let enough fuel to flow to meet the demand. A bad fuel pump gave me the same symptoms but you could also hear the inconsistent hum from the pump when engine was running. A bad Bosch fuel pump made in china that was less than a year old was the culprit.

[lindbhr]

Vick - my 72 had your same issues. It was the CDI....Good Luck!

[HarryD]

Sounds like it might be an overheating problem. When it cuts out put your hand on the CDI and Coil. If warm, put some ice on it and try again. If it starts right up, that is your failing component.

I had a similar issue with both my long gone Triumph Spitfire and more recently with the Permatune in my 911.

[vick]

Thanks all for the tips on CDI and/or coil. The intermittent occurrence has made it hard to pinpoint

The heating point is a bit confusing because it ran solidly all day yesterday including some stop and go traffic, never stumbled when the motor ran above the cruising temp. But maybe a failing component that’s finally tipped over

[HarryD]

Originally Posted by vick

Thanks all for the tips on CDI and/or coil. The intermittent occurrence has made it hard to pinpoint

The heating point is a bit confusing because it ran solidly all day yesterday including some stop and go traffic, never stumbled when the motor ran above the cruising temp. But maybe a failing component that’s finally tipped over

Exactly. It takes time for the heat soak to finally get the failure to occur.

To diagnose my Spitfire, I drove around with an ice chest. When it failed, I ran out, packed the electronics in ice (at the base of the distributor) and it fired right up. Did it 3 times to confirm. Was quite the sight at the traffic light.

[aldente]

if/when you replace the coil, avoid the ones from Brazil

I like the ice cube for testing, but dunno if it will get him to Boston