Car stalls without warning

J

jimrat

Low Mileage
Hi

My X19 will idle happily, but after 3-5 minutes driving around town, it stalls without warning and will not restart. I have to wait 5 minutes, then it will start again, and the cycle is repeated.

It’s a 1500 Euro X1/9, standard except for electronic ignition and electric fuel pump. It’s just coming out of a 3 year nut-and-bolt resto, so absolutely everything has been apart.

It feels electrical because it stops suddenly, but after its stalled, the dash battery light is on, I can hear the electric fuel pump whirring and there is still +12V to the coil. The ignition switch and battery are new, and the alternator is kicking out 14.4V.

All the ignition parts are new, including the coil. I fitted a spark indicator on one of the plugs and the spark is bright and even. Static timing is set to 5 degree BTDC and the centrifugal advance checks out. The car pulls nicely.

I’ve checked the fuel tank pick up for dirt, and the fuel tank is not under vacuum. The fuel filter is full of fuel. The carb has been cleaned and a refurb kit fitted, and the float level is set correctly. The spark plugs are not fouled. The cooling system is in good shape, and the temp sits at 90 with the fan cutting in and out OK

One thing I have noticed: if I remove the oil filler cap when the engine is running, I can see oil flying around inside the rocker cover, and oil will spit out of the cap. Is this normal – I’ve never had this on any other car?

This has been going on for weeks, and I’ve checked and rechecked fuel, spark and air several times- I’m completely stumped by this. I cant believe it’s the fuel vaporisation issue, as it’s winter here in the UK, and I have the electric fuel pump fitted.

Any ideas?
Thanks
Jim
 
Oil flinging about with the cap off is normal, just ask my buddy who did a club drive with the cap off and completely coated the engine bay in oil.

Drive with the gas cap off and see what happens.

I had similar problems with a carbed X. It would die so suddenly it had to be electrical and chased that for a week. Then hooked up a clear fuel line to the carb with the engine lid off and as it died I could see no fuel in the line. Turns out the pushrod on the mechanical pump was a marginal length and as the motor heated up tolerances loosened up and the pump no longer worked. I realize you have an electric pump but just showing a quick die off can be fuel.
 
What kind of electronic ignition do you have? Many of the aftermarket ones are not noted for their reliability, especially if they are old. The symptoms you described sound consistent with electronic ignition problems I've seen before.
 
Jim,

Hard to diagnose but I would start by checking fuel.

When you did the restore did you change all the fuel lines too? How is the filter in the carb?

When you are in the stalled and won't start mode, take off air filter cover and try and start it with some fuel sprayed down the carb (easy start/WD40 petrol if you have it). If its fuel then it will run for a while.

If it's fuel you have to see how far the fuel is getting when it won't start, if you can find some fuel safe clear lines to test that might help (not heard of this before carl's post) or pull a fuel line off and see if fuel is coming out. I would start at the fuel return line and work backwards.

If it's spark, do you have the old parts to swap back to try?

idle ok but dies of driving sounds to me like fuel starvation but hard to diagnose remotely.

This is a take you time and be methodical and I am sure you will find the problem. And first step is to see if its fuel or spark.

Best of luck
 
Hi

Thanks everyone for your replies. The electronic ignition is a new Magneti SE100CX distributor unit, as used by lots of people on here. All the fuel lines are new, and the carb bowl filter is clear.

Apart from the float level, is there anything in the carb which could cause a sudden stall?
 
Try cranking the engine right after it dies and see if your "spark indicator" is still showing spark. If it does not, the 5 minute recovery time (can be 5 to ~15 min) might be a clue as I've seen that behavior before on a Mercedes Bosch igntion module and on an aftermarket unit. In both cases, the problem ended up being due to a contaminated NPN transistor that was used to ground the coil (electronic points replacement).

There was a cleanliness problem back in the 70s for the semiconductor industry that impacted the reliability of transistors, particularly NPNs used in power applications. Humans are full of sodium chloride (salt) and it was hard to keep it away from devices during wafer processing or packaging the parts. Back then, there was very little automation but lots of human contact. Having NaCl on top of the device does not start to affect things until bias is applied. When that happens, the positive Na ions get attracted to the transistor base region (P type for an NPN) and the collection of these positive ions will attract enough negative electrons to the base to convert it from P type to N type. This means that the transistor is now a resistor! After the voltage is removed, the Na ions will slowly drift away from the base and the transistor will operate until the issue reoccurs. The amount of time it takes for the Na ions to drift away is a function of temperature. The higher the temperature, the faster the device will recover.

On that Mercedes Bosch module, we were seeing about a 5 to 10 minute recovery time. My friend who owned the car went to what was supposedly the best Mercedes electrical guy in SF, spent hundreds of dollars replacing stuff without fixing the problem. We decided to "instrument" the engine ignition system to try and figure out where the failure was occuring. There were several light bulbs and meters used to monitor a number of nodes in the ignition circuit. The light bulb wiring came out between the back of the hood and windshield, and we got plenty of strange looks from people passing by. The smoking gun moment came when the engine started to die with all the correct voltages showing but zero reading on the dwell meter. That meant that the current was not being switched on and off in the coil primary and therefore no current was being induced in the secondary, therefore no spark.
 
The 'new' Magneti distributor is definitely new old stock - when I initially fitted it I wasn't getting any centrifugal advance. I had to strip it down and free up the mechanism as moisture had got in there. I wondered about fitting indicator bulbs in the coil and fuel pump circuits so I could see what is going on. Maybe I'll give that a try
 
Since your car starts out running OK, I would be surprised if it was the float level since it is not likely to change during driving.

Is your new electronic igntion compatible with the coil you are using? That issue ofen comes down to where is the ballast resistor. For the 1300 cars with the points ignition, Fiat used a ballast resistor built into the coil. On the 1500s, they went with an external ballast resistor. There are some electronic modules that have the ballast resistor built in. In most cases, there will need to be a ballast resistor somewhere or there will be too much current causing the coil and/or the ignition module to overheat. You might want to check that out if the car is shutting down after 5 minutes.
 
My car is 1984 UK spec and doesn't have a ballast resistor, or at least not one that I could find. I spent ages trying to find info on the right coil for the SE100CX dizzy - I think the coil I'm using has a 0.8 ohm primary resistance. Neither the coil or ignition module get hot to the touch...
 
Per the 79 - 82 Fiat manual, the 1500 coil has a primary resistance of 1.1 to 1.7 ohms and the ballast resistor is .85 to .95 ohms. That is a total resistance of 1.95 to 2.65 ohms. You might want to check the specs on the SE100CX to see what it is expecting for total primary resistance as 0.8 ohms would be too low for many units, including the stock Bosch.
 
No, nothing. According to the seller it is listed as fitting Fiat various 1.3 Strada, Ritmo & Uno models, and so I matched the coil to one of them.
 
Saw a similar behavior on a spitfire. Ended up being a bad coil to distributor wire. As the engine warmed up, this wire would lose connectivity and engine would die. Ran perfectly when cool.
 
jimrat said:
No, nothing. According to the seller it is listed as fitting Fiat various 1.3 Strada, Ritmo & Uno models, and so I matched the coil to one of them.
Click to expand...
I ran this distributor when I had my original engine. I ran it with the original coil and that worked fine. At the time I didn't even realise the difference with coils. Anyway I doubt its a bad combination of parts.

I thought from your original post when you had the stalled/no start mode that your spark indicator was showing a spark?
 
I had this and in the end it turned out to be the ignition switch! I could crank it for ages but it wouldn't fire up. It was an 87 car in the UK with Lumenition electronic ignition. Do the brown wire mod too while you're faffing about.
 
Hi, can someone please confirm jet positions. 3=primary idle, 5 = primary main, 7 = secondary main, 8 = secondary idle?

This youtube video (3 minutes in) says 3 and 8 are swapped


1711996240462.png
 
jimrat said:
can someone please confirm jet positions. 3=primary idle, 5 = primary main, 7 = secondary main, 8 = secondary idle?
Click to expand...
That's correct - you can check by spraying carb cleaner (with the little tube) into the idle hole and you can see it first start to come out the adjacent main. Not sure where the guy in the video got his info from :eek:
 
Alex(Tenerife) said:
I ran it with the original coil and that worked fine.
Click to expand...
@jimrat Might be worth sticking back the stock 3 ohm coil as Alex says - it could be the module isn't meant to run with 0.8 ohm and is shutting down to protect itself. But then again, you say the module isn't getting hot? 0.8 is generally correct for the separate HEI modules like in the AEI200 packs on 124s and later Montecarlos. There's no ballast resistor on the euro/uk cars that had the Marelli factory 135/155/178 distributors.
 
jimrat said:
Hi, can someone please confirm jet positions. 3=primary idle, 5 = primary main, 7 = secondary main, 8 = secondary idle?

This youtube video (3 minutes in) says 3 and 8 are swapped
Click to expand...
You might want to download the manual for your car from the Wiki on this site. On page 10-87/88 it has a complete parts diagram of the carb with everything labeled. There is also a chart showing what the values of jets, etc. should be.
 
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