Intermittent Hard Starting 84 FI

[AJgraham02]

Hey guys another update. The fuel pressure regulator did not fix my hard start and running problem. I replaced that fuel line while i was in there and out and then decided to double check my grounds going to the ECU. All measured good there with the Bosch L jet guide but when I plugged the ECU back in it ran great. It idled for 30 minutes plus. I restarted it 4 or 5 times no problems at all, But poor weather kept me from driving it.
I went back out a couple days later and the problem was back. I work on newer cars for a living but I never thought this Fiat could kick my butt this hard haha

[spider2081]

Have you removed the spark plugs right after the car failed to start? if so are the wet with fuel?
Have you inspected the inside of the distributor cap and rotor?
Have you measured the voltage on the pink ignition coil wire for battery voltage when the car is cranking and not starting?
Did you measure the coolant temperature sensors resistance at the ECU connector pins? 5 is ground 13 is the sensor. should be 2000-3000 ohms when engine is cold. 200-400 ohms when engine is hot.
If the car acts flooded when the engine catches after excessive cranking it could be lack of spark. The fuel system could be working and the filling the cylinders with fuel even fouling some of the spark plugs because of weak or no spark.

[18Fiatsandcounting]

One thing you could do is connect a timing light to one of the spark plug wires, or better yet, on the wire from the coil to the distributor. When you crank the engine, it should flash regularly even if it isn't starting. No flashes = problem with your ignition system. Flashes OK = likely a fuel issue.

-Bryan

[rridge]

First general rule of engine diagnostics. If an an engine related system shuts off suddenly, particularly when going over a bump, suspect the electrical side, including grounds and ignition switch.

Second rule of engine diagnostics. When a fuel supply problem are suspected, first rule out the ignition. It's much easier to do and at least half of all "fuel problems" are mis-diagnoses. That's that's doubly so on an old L-jet FI system which relies on a solid ignition signal to time the injection.

[AJgraham02]

I appreciate Everyone's advice, I am going to bring home a tool bag and start going through everything again to see if I missed something.
The I did pull the plugs after the last no start and they did have some fuel on them, The cap and rotor I replaced recently while trying to diagnose this problem as the cap was worn quite badly. I know i have power at the coil with the Key in the On position but I will check for a voltage reading while cranking tomorrow. I feel like its part passed maintenance and sitting as well as me missing something simple i should have otherwise caught

[18Fiatsandcounting]

The cap and rotor I replaced recently while trying to diagnose this problem as the cap was worn quite badly.

There are subtle differences in distributor caps and rotors between the model years, so are you sure you have the right cap and rotor? Sometimes auto parts suppliers make mistakes, too.

-Bryan

[AJgraham02]

I will have to pull the caps and compare Everything, Makes me glad I kept the old one just in cause, I wasn't aware of any differences between them

[18Fiatsandcounting]

Good idea. I always keep the old parts until I'm sure the new parts work. Check the height of your new rotor, and make sure it seems to be at the same level as the contacts inside the new distributor cap. Sometimes the "heights" are different, and the spark can't jump the gap.

-Bryan

[RRoller123]

I got a cap once from the store, it had the 4 copper contacts not colinear with the rotational axis! Visually WAY off, like a 0.01" rotational axis difference from side to side! I assumed that the tooling that holds the contacts during injection molding slipped or it wasn't setup correctly, whatever. Defective cap. I showed the store manager, he grumpused a little and gave me another one... and put the bad one back on the shelf.....

[spider2081]

I re-read this entire post and did not see that you have removed the connector for temperature sensor in the coolant "T" and inspected, cleaned and reinstalled. As I mentioned earlier the troubleshooting manual suggested measuring the resistance of the temperature sensor from the ECU's connector. This is so the resistance of the connection can be checked along with the resistance of the sensor itself. One simple test is to start the car and wiggle the connector on the temperature sensor and see the engine rpm changes as you are moving it. I think most Spiders fuel pressure is in the 28-35 PSI at idle.

[AJgraham02]

Sorry about that, Sometimes i forget to add things i fixed or tried. The connector on the coolant tee was bad. Half of the lip to lock it on was gone and the PO had it zip tied to the sensor. I replaced it with a new pigtail, doing one wire at a time to prevent mixing them up. I do remember measuring the resistance right at the sensor at the time, but the measurement is not in my notes I will have to check it again.
Unfortunately it seems like my project is going to be on hold for a bit due to the pandemic and where i store my car but I will keep everyone updated as I sort through all this.

I did try to start it again today and it did catch much easier than it has been. But it feels like its only running on a couple cylinders. I have spark on all four down to the plugs, I'm going to pull them all the next chance I get and see if its a gap or fouling issue

[RRoller123]

Spark to all 4 without a miss implies the injectors possibly aren't doing their job. At the risk of repetition, have you had them cleaned or replaced? Attached a Noid light on each to determine if they are firing? You can listen to them individually with a mechanic's stethoscope and it works surprisingly well! You can very clearly hear the click when and if they fire.

[wizard124]

Bad flow from the fuel pump? I would disconnect the feed into the fuel rail and pump fuel into a 5 gallon jug. Look for good volume and steady flow. Blow out any crud in the line and test fuel pump function.
Intermittent function could be bad or overheating fuel pump or a failing dual relay..
I'm a bit rusty but one side of the dual relay drives the fuel pump; the other the ECU grounds or fuel injectors.
If your engine gauges all die simultaneously with your engine then I would suspect the ignition switch.

[AJgraham02]

When it dies I still have the fuel gauge and lights on the dash. Power at the coil never drops from that 12v either so I'm leaning away from the ignition switch although it was a thought. Next time i get to the shop where I keep my car I'm going to drain the tank(Fuel is getting a little old) and replace all the hoses by the tank and blow out any junk I find in the lines.

I also want to pull the plugs and see if one is fouled and check the injectors with a node light
I feels like when it runs, its only running on 1 or 2 cylinders, It almost sounds like an old Hit and Miss engine

[spider2081]

and see if one is fouled and check the injectors with a node light

I think a node light is used to tell if the ECU is signaling the injector to open. If an injector is stuck open or closed I don't think a node light can tell you that. I like to listed for the injector click with a stethoscope or a long screwdriver. The injector makes a very distinct click when it opens. All 4 should sound the same.