1980 fiat fiasco wiring question

[Slawnski]

I have a 1980 fuel injected fiat. Bought this one as a parts car but saw more potential in it than that of a donor car. I’ve replaced the fuel tank, fuel pump, fuel filter. I’ve got 125-130 compression on all cylinders. 40 Psi fuel pressure. Engine started but only just- I saw a good leak at the water pump so dove in and replaced the pump, tensioner and timing belt. Everything is now back together timed properly. I have checked and replaced valve shims to get correct gap(s).

I have a no start situation now. I’m assuming I have neglected to plug something in correctly- I get exactly one spark on a spark plug plugged into the lead and grounded to the engine. One spark only- then no spark - every time I return the key to off and try to start I get one spark then nothing.

Couple questions:

Do I need fluid at the tee fitting where the sensor is in order for the engine to fire?

I have two sections of my wiring harness that look like they should have relays? Any idea if I’m missing something here? I don’t believe this effects starting as engine ran prior to me pulling stuff out to get the belt and pump replaced

https://imgur.com/a/WIJ1ZO0

Other ideas on where I went wrong?

Thanks for any help you can offer

[Slawnski]

I should add that the relay panel below glove box is missing one relay-

https://imgur.com/a/UCJ9VPM

My other fiat has this relay in place. It is a Bosch 0332204107

I’d look for the parts of the wiring harness on my other fiat but I’d have to dig pretty deep- the wiring in the project fiat is all laid out with no center console in place.

[TX82FIAT]

I would get two things and read them over. 1. Brad Artigue has at one point put out a very good Bosh L jet troubleshooting guide. I think you can find it in WWW.Mirafiori.com. I would encourage you to register as a user and get its full content open to you so you can get the troubleshooting guide. 2. Since the dash is out, get a wiring diagram and get familiar with what each relay does and what circuits are involved. Once you get the car running there will most likely be other electrical gremlins to tackle so don't put the dash back in yet. A lot of electrical issues with these cars results from poor grounds and poor connectors. Cleaning all grounds and connections points often brings things back to life.

[spider2081]

I have two sections of my wiring harness that look like they should have relays

Those 2 connectors look very much like the electric window switch connectors. Fiat prewired some Spiders for electric window even though the car was delivered with roll up windows.

I think 40 lbs fuel pressure is a little high but probably not the issue. I think it would drop a little if the engine was running.
Where did you place the spark plug for its ground on the engine. The valve covers on the twin cam engine is isolated grom the engine ground by its gaskets. I like to use the hood latch on the firewall when testing for spark.
Did you inspect the pick up coil in the distributor and measure its resistance? The pick up coil should measure about 750 ohms at its 2 pin connector that connects to the ICU
Have you measured the resistance of the coolant temperature sensor in the coolant "T" It should be about 1500-2500 ohms for a cold engine.
Many suggest measuring this resistance at pin 13 of the ECU so the sensors ground and wiring to the ECU are also tested. Also with the coolant sensor connector disconnected neither pin in the sensor should measure to ground. It is possible for the censor internals to short to its case making it inoperable
If the connector on the coolant temperature sensor is not making a good connection or is disconnected the ECU goes full rich flooding the engine.
Will the engine start if you remove the brake booster vacuum hose from the intake plenum and spray starter fluid into the plenum?

Just some thoughts hope it helps.

[Slawnski]

Found one issue tonight- I had pinched one of the internal wires between the distributor and the cap. The wire was grounding to the distributor body. I’m getting normal spark now. I’ve joined http://www.mirafiori.com/ I’ll dive into their library for the fuel injection troubleshooting.

I thought 40 psi was a little high myself but was told by the supplier it was ok not too high.

The motor kicked over a bit after I ungrounded the wire in the distributor but would not stay running. I’ll recheck timing tomorrow as well as ohm out the sensor.

Not sure if it matters but the timing was waaay off when I received the car. Almost 90 degrees before TDC. Initially it ran but very poorly. When I put the new timing belt in I clocked the oil pump drive pulley, lined up the dots on the cam gears and was at the timing mark on the crankshaft pulley.

To be certain : I am setting my timing to cylinder #4 correct? I know it’s normally ( other vehicles) timed with #1 at TDC but saw or heard fiats use #4.

The power window explanation makes sense-

I’ll keep plugging along and post updates.

[18Fiatsandcounting]

To be certain : I am setting my timing to cylinder #4 correct? I know it’s normally ( other vehicles) timed with #1 at TDC but saw or heard fiats use #4.

You are correct, in a sense. When the timing marks on the crankshaft are aligned with the 0 degree mark on the timing pointers, cylinders #1 and #4 are both at TDC. When the camshaft pulley marks (those little holes) are aligned with the timing pointer for the cam pulleys (and the nub on the cambox housing at the front), cylinder #4 is the one set to fire, so the ignition timing should be set using the spark plug wire for #4.

In practice, you can set the ignition timing using either the #1 or #4 plug wires. For #1, this would mean the camshaft pulleys are 180 degrees out from their timing marks, while if you use the #4 plug wire, those cam pulley marks will be aligned with their pointer. It's more accurate to use the marks on the crankshaft though.

I hope that made sense...!

-Bryan

[Slawnski]

Thank you Bryan. That does make sense.

[Slawnski]

Ok so a couple updates: using ether to try to get some life did nothing.
Pulled off the cover- checked my timing marks- I’m still good

Downloaded fuel injection diagnosis manual. Holy moly! I’ll be going through the diagnosis process in the coming evenings and I will update as to what I find.

Thanks for the posts and the advice. Not giving up on this car.

[Slawnski]

I need a clarification please. I’m going through the checklist. Fuel pressure 35 psi- check
4)I need a better way to check injectors but a voltmeter rolls around with different values I assume I’m ok - check
5) Coolant temperature sensor resistance - 2495ohms-check
6) thermo time switch- no light. Double relay check 86a-86- no light. Ugh
7- I did not check cold start valve - I assume it’s pointless given check 6
terminals 6-8 362 ohms terminals 7-8 282 ohms terminals 8-9 200 ohms. All signs point to bad air flow sensor.
9) fuel pump voltage good
10) voltage output to fuel pump at relay set - no light
11) voltage input to relay- check
12) voltage input fuel pump relay- check
13) test -check
14) test- check
15) test- check
16) test- check
17) test - check
18) test - check
19) test- check check - check

So at this point it looks like I need an air flow sensor at very least

[Slawnski]

https://i.imgur.com/QDFssGM.jpg

This is what I need clarified. The result of this test is a light on situation. Is there a typo?

[spider2081]

This is what I need clarified. The result of this test is a light on situation. Is there a typo?

I don't think there is a type o.
There has to be voltage into the relay for there to be voltage out of the relay to turn on the fuel pump.
You state you have 35 psi fuel pressure. That would indicate the fuel pump is operating normal.
Unless the dual relay has be bypassed by a previous owner meaning the fuel pump is hot wired, having fuel pressure usually eliminates testing the dual relay as having pressure means the relay is working.
the resistance you measured at the coolant "T" temperature sensor is on the high side I usually measure around 1500 ohms. Did you measure it at the sensor terminals or at the ECU connector. I think its recommended to measure at the ECU connector pin 13 to ground. I use the stud that the plastic nut goes on for the ECU retainer for the meters ground connection.
Have you removed the spark plugs and inspected them?

[Slawnski]

The line in the text of the test states that if the light comes on I need to replace the dual relay. If I understand it correctly when the light comes on it means I’ve passed that particular test and there is power going through the dual relay for the fuel pump. I should not have to replace the dual relay.

The spark plugs in the engine now are new the old ones looked relatively normal if just a bit carboned up.

I will measure 13 to ground tonight

I just don’t understand how I could have spark, compression, and still not get the engine to fire - if briefly on a prime of ether. I know I’m getting fuel to the fuel rail at the proper psi. I could understand it’s starting and not wanting to continue to run. But it’s a bit befuddling at this point. Has anybody rebuilt their airflow sensor before? I’ll search the forum for that answer. I’m looking at a replacement airflow sensor and it’s pricey.

[spider2081]

The line in the text of the test states that if the light comes on I need to replace the dual relay.

I don't have that test procedure to read however I am assuming the test is one of a series to isolate why the fuel pump is not running. Being as you have normal fuel pressure, in my mind the fuel pump is running.

if briefly on a prime of ether.

I remove the brake booster hose from the intake plenum and spray starter fluid in at opening for the booster hose. I spray for a couple seconds so there is enough starter fluid for all cylinders to fire.

If questioning the air flow meter:
can you move the flap with your finger through the large opening for the hose? Have you removed the black plastic cover to visually inspect the the parts and operation? I use a pick bent at a right angle to remove the glue and then a thin flat bladed screwdriver to pry up the cap where the connector is located.

[Slawnski]

Pump is running- I’m good there

The flap operates smoothly on the air flow sensor.

I’ve looked under the cover and the components look like new- doesn’t mean they work. I’ll need to find procedures for how to test the components. They sell rebuilt units - so I’m sure it is rebuildable. I’ll swap the airflow sensor from my running fiat to this one and see if it makes a difference. Any chance I can do damage to the known working unit by plugging it in to the non-running vehicle? Right now 50% of my Fiats run smoothly I’d like to keep it that way at very least.

I’m going to focus on my ignition system again tonight- odd that it just doesn’t even fire once.

[spider2081]

Any chance I can do damage to the known working unit by plugging it in to the non-running vehicle?

most of the Bosch fuel injection components are very forgiving when it come to one part causing another to fail. I have changed the Air flow meter many times chasing a problem. Never had one develop a problem from putting it in a non running car.
I like checking the fuel pressure on fuel injected cars. its pretty simple to disconnect the fuel line from the cold start valve and connect the fuel pressure gauge there.
I find very often the coil pack is easy to swap and is a problem.