L jetronic / inertia switch

[MNspiderman]

I have the two wires that come out of my inertia switch. One goes to the dual relay. The other one takes a turn and goes into the firewall. Well I have no power to these wires. Where does the wire go to that goes into the dash? ignition switch? fuse box? relay? I literally ripped my dash off to try to find where it goes and to no avail, I cannot trace it once it goes through the firewall. I have been banging my head over this for about 4 months now. If your really into the bosch thing. I have NO continuity between pin 50 and relay number 88a. Its killing me. Whats this means is.... My car runs extremely rich, chuggs and only works when i take off the afm cover and manually hold the "points" open so it will quit squirting fuel into my cylinders. Assuming the fuel pressure keeps building up because there is nothing to shut the dam thing off. Arggggg my auxilary air valve works, my thermo time switch is good, my cold start valve doesnt squirt, my water temp sensor works. The car is an 84'
I can operate an ohm meter pretty well. Continuity is a no brainer. I even did a continuity on all my grounds which are terrific. I could use anyone's two cents worth about now... Ya, my shop manual is like 3" thick and its terrific. Except when it says if i have no continuity between pin 50 and 88a on the dual relay. It says there is a "break" in the line. DUH... But it doesn't say where that wire goes too. Thats whats killing me...

[rlux4]

What is an inertia switch? I may be showing my ignorance here, but I've never heard of it. Unless it also goes by another name?
Ron

[So Cal Mark]

Ford used an inertia switch to turn off the fuel pump in case of an accident. The pump switch in the afm keeps the pump from running until there is airflow. I suppose you could call it an inertia switch since it stops fuel flow if the engine is off.
The pump has to run all of the time the engine is running, so if you're opening the switch to lean it out you are just running it out of fuel.
Have you checked the injector pulse rate to determine if it's rich due to extended injector on-time? Have you checked the pressure regulator to see if it's leaking? Other than that only the cold start injector could make it run rich.

[pope]

I dont know of a pin 50 on a Fiat Spider. Are you sure you are not talking about terminal 50 on the ignition (start)? That goes to 86a on the dual relay.
The wires on the AFM go to the dual relay and the ECU under the dash.

Like Mark said, the fuel pump continually runs and the fuel pressure regulator on the end of the fuel rail controls the amount of fuel pressure. Make sure the small suction tube that goes in the fuel pressure regulator is operational. Also check that the other end of that small vacuum tube, where it connects to the intake plenium has an opening in it and is not clogged up. It is a pin hole and can easily clog up causing improper pressure in the fuel rail.
Just to be clear, it is the plenium metal nipple that gets clogged up, not the rubber hose. (unless the hose is brittle and cracked). You might have to insert a thin wire into it to see if it is clear.

[MNspiderman]

Oops in my frustrated condition. I should have mentiond that this is for my Alfa Romeo GTV6. But the exact same principal is in effect being they both have L jetronic injection. Fiat, Lancia, Alfa, Porsche, and probably others use this exact set up. Just some of the parts are located in different areas. Maybe i should move this to off topic because its really not a fiat but i don't know how to do that. So let the saga begin. when i got this car. i didn't know it but the P.O. put a jumper between the afm pins that are connected to the fuel switch. He also added another realy between the vehicle side of the combirelay and jetronic relay. This is a temporary thing because I want it right. So I pull off the extra relay and the jumper wire on the afm. So now I have no power to the fuel pump. Keep in mind my pressure regualor is new, all grounds are terrific, all ohms are where they should be. etc, etc etc. My educated guess is there are wires going somewhere that aren't connected to something else. If i push the afm flap (yep the cover is off) and the points make contact. no fuel. its a dead circuit. just had to state that. So in the book. it says measure voltage from 88z to ground = GOOD. measure 88b to ground = NOTHING. = pin 29 on ecu. I would also like to quickly add that there is a little diod or resistor thingy on the fuel switch in the afm which goes from the second termial to the third terminal insided of the little black box. Well if i put my ohm meter across it. Nothing happens. but then I don't know if something is suppose to happen. I figured i should get some kind of reading. but sometimes zero is what your looking for on an L jetronic. Afm flap works, when pressed and released, ohms go from 8ish down to 1ish. which is good. couldn't there be a bad device such as an ignition switch? ecu? ignition module? and thats why it seems so screwed up? Oh ya, the thing i called an interia switch is also called a safety switch or a fuel cut off switch.

[pope]

Although L-jets are supposed to be the same from maker to maker, I dont know of the nuances between cars.

When you push on the flap, the key is in the ON position, right!

[MNspiderman]

I'll end this thread, I don't know how to delete it being its not a true fiat thread. I am starting to get some answers at the http://www.alfabb.com site. Thanks for the help. for the curious, this is what i was talking about.

[pope]

Those are ground wires, they add ground when the safety switch is engaged and subtract ground when the switch is open. The Bosch FI system works that way. Things turn on and off by adding and subtracting ground.

[So Cal Mark]

I'd suggest you restore the system to the way it was originally wired, otherwise you will go crazy trying to figure out why and what the PO did. People usually do "repairs" like that because they don't understand how the system works

[MNspiderman]

Mark, thats exactly what i am trying to do. the dude on the alfa page said that those wires to the safety switch are suppose to be "hot" but they aren't. he said that 88d goes through there with power directly to the fuel pump and that the inertia switch is the cut out switch in the line, which i already knew that. my car is running without that system. which tells me that wires must have been snipped and swapped to send power to the pump not through the inertia switch wiring. what a nightmare. and lately my fuel pressure is over 50psi so my engine is chocking on its own fuel. I have no blockage going back to the tank, air compressor in return line verified this for me. fuel pressure regulator is brand new. so apparently the old regulator was good too because it didn't fix anything. It remained the exact same when i swapped it out for a new one. vacuum hose to regualtor is good, no blockage in intake, afm works excep the part where the points turn on the fuel pump. I have an L jetronic book for alfa, its 3" thick but alot of it says hook up the bosch thing and if you get a green light its good and if you get a red light its bad. just great. i've done continuity tests so the grounds are great, the sensors are all at the proper ohms. Its just that some wires somewhere else not under the hood have been crossed i think. I think i am venting here a bit out of frustration. I must have 60 man hours tracking this gremlin down.

[So Cal Mark]

why do you feel 50 psi is too much?

[MNspiderman]

because my regulator is suppose to be operating at 36psi's at idle and i have between 50 and 60psi's. do you suspect something else is causing my injectors to keep on dumping fuel in my cylinders. i was thinking the high pressure is causing the excessive fuel dumping. I had to run 30' of exhaust hose away from my garage or you would literally die in 3 minutes if you could even last that long.

[pope]

The Fiat has a pressure of 37 to 43 PSI, and that is for a 4 cylinder. It just seems to me that if the gas regulator is working correctly, than the pressure is correct. Were the fuel injectors swapped out for larger volume ones.
The gas fuel line that returns the fuel from the gas pressure regulator to the tank could be blocked causing a back pressure.

[rlux4]

Is the fuel pressure above 50 psi before or after the regulator? The pump will put out that much, but the regulator should drop it down to about 30 lbs. However, even if your pressure is higher than that, the duration of opening would be reduced to compensate by the ECU.
If the PO didn't bypass the dual relay, with the key on and the AFM flap opened the green with black stripe wire coming out of it should have 12V. (It goes to the fuel pump.)
Is your cold start valve stopping as it should? This would be a source of unmetered fuel.
Excess fuel could also be from leaking injectors.
Ron

[So Cal Mark]

with the various changes the PO did, does it have a replacement fuel pump?