Michigan had smog testing for a period of time; if your vehicle failed you were required to have all emissions equipment in place and perform a “low emissions tune up” to identify what was wrong and make sure any adjustments were to specifications. The cost was capped and went to the shop, as did the test fee. It was not a revenue generator.
Actually it was a revenue generator for the shop, if everyone inspecting the vehicle did the inspections as mandated by the state. The problem is some shops used to would pass a vehicle without actually inspecting the vehicle.
In NC some counties have emissions testing some don’t based on how populated the county is and now the state computer reads from the OBD port. It automatically fails the vehicle if the check engine light is on or certain codes are read.
No, didn’t generate any revenue; the people with cars that failed had no money. The cost cap didn’t cover the time to diagnose, let alone adjust anything. The people that had money fixed their vehicles before they needed licence tabs. Probably 98% passed anyway, as Michigan was just an idle sniffer and was before OBD.
NO, as pointed out earlier (24/43, Sep ) and some other times, the Tach signal comes from Bank A, Coil A, not the Bank A power amp as shown even on your electrical diagram - Maybe a stronger magnifying glass or glasses might Help?
I have 4 different references for Marelli cars, all of which say the same thing. The tachometer feed is connected to both the A bank coil and the A bank amplifier, the WN feed wire is common to both, joined at the coil terminal. Or are you saying all the schematics are incorrect? I don’t have a Marelli car to check direct continuity from tach->coil->amp.
That means the Marelli cars have a 6-cylinder tach, right? I was just reading on another thread a reference that said the signal for the EFI, the transmission, the fuel pump controller, something else to do with fuel, and the tach all come from the Marelli ECU, and it’s a 6-pulse-per-crank-rotation signal – meaning it would require a 12-cylinder tach. So I guess the Jaguar literature is up to its usual shoddy tricks.
I wonder if there might be a difference between the 5.3 Marelli and the 6.0 Marelli in this regard. I’m pretty sure the reference I was looking at was for the 6.0.
So we have a diagram from jayjagjay above showing the tach getting its signal from the A bank coil, and this diagram from sbobev showing the tach getting its signal from the Marelli ECU. And I guess I’m being skewered for not reading messages carefully enough.
Engine speed is not the tach signal. This is the waveform you asked for, which the Marelli ECU generates and sends to the Lucas EFI box.
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It says it is used by the “Driver’s Tachometer.”
I give up. These are the input/outputs of the Marelli ECU:
And this is the corresponding electrical diagram:
I made the same assumption as @Kirbert, the description of the wiring said the tachometer was driven by the PCMI, which I guess must be the Marelli ECU? The electrical schematic however matches all the other Marelli ones I have seen where the tach feed is taken from the amp output/coil input.
Ehhhh, never had reason to look at it that close. But now that I did, I came to some conclusions:
- Don’t trust the Jaguar wire color coding – the 1992 wiring diagram (WD) color codes for the Marelli does not match the color codes for the Marelli in her ’92 XJS. Both the A and B coils use a white wire from tach signal circuit in the coils to the A & B Power Modules – not a white brown (WB) for coil A, or a white black (WB) for Coil B.
- It is true that the tach signal circuit is common to each coil and power module. Continuity can be found in each case from the white wire (outer contact of the two adjacent contacts – the center contact drives the tach - of the coil plug to a singular terminal in the power module plug.
- I don’t know what goes on inside the triangles of the Amp Modules – don’t care, have other stuff to keep me busy and all is working well.
- If someone feels better stating that the pulse that drives the tach can be taken at the power module, it could, but why bother to do the mod when a connection to drive the tach is already provided at each coil, and the plug to do so is located at the A Coil. Anyway without actually knowing, I suspect that the actual pulse shared by the Coil is generated by the coil, and that’s why they put the connection there.
That’s the reason I believe you should connect it there at the coil.
English is not my mother tongue but driven and used don’t have the same meaning, don’t they?
EDIT: Because every time 6.0L is referenced to, confusion arises - here is the “correct” section of the manual - for 5.3L Marelli. TH400 transmission, so all the reference to transmission retard and other similarly unknown many functions are not mentioned.
OK, that chart confirms that the signal for the tach comes from the A bank coil which would be a 3 pulse/crank rotation signal. It appears that the reference that sbobev posted must be incorrect.
But, that diagram doesn’t seem to show any signal to the EFI system at all – unless it’s the one labelled for “fuel pump control unit”.
Because the pulse at the Marelli ECU is 6 pulse/crank rotation while the connection at the A coil is 3 pulse/crank rotation. So, if someone wants to toss the Marelli over the hedge and retrofit a Lucas CEI, how do they drive the tach? There is no 3 pulse/crank rotation signal to be had on a CEI. I suggested one idea might be to leave the Marelli ECU and sensors in place just to drive the tach, which would seem kinda silly but would work and wouldn’t cost much. It’s also been suggested that it’s easy to create a PCB that divides such signals by two.
OK, we all know that Kirby can be stubborn, at times. Here, figure 25 - engine management. Pin #18 is input from the Marell ECUi.
This signal is supplied via the shielded wire which we were discussing yet again just a few days ago.
Oh, I had no doubt that the EFI gets its trigger signal from the Marelli ECU. I just thought it was rather marvellous that it wasn’t shown on that schematic of the Marelli wiring.
Not shown? The oval area and the output from pin #24 in my post above
The little numbers are references to the figures 25 and 26 btw, everything is there.
So you’re saying the line labelled “Fuel Pump Control Module” is actually the EFI trigger signal? Is there a “Fuel Pump Control Module” in this car? Or is that Jaguar’s terminology for an EFI ECU?