Bill's EFI Drama AKA A Game of Name that Component!

[mentalite]

Sounds like fun doesn't it?  The winner receives a free glass of water at their favorite restaurant!

I started through the process of tracking down my fuel pump and richness condition by going through the wiring harness and checking all of the connections.  Man, is this sage advice from ZedHead and others!  I found corrosion in many places (still not done), the worst on the thermostat or coolant sensor housing connections.  Of course since I am a complete rookie this leads to the inevitable list of questions.

I started at what seems like the most logical place - the ECU.  I started here to follow the harness to it's many terminations.  Stumble #1 was an almost immediate link to a box just above the ECU which I believe is the fuel injection relay.  Should I pull the plug on this and check for corrosion?

The harness runs through the firewall and goes into this guy just below the power brake booster.  Dropping resistor?  Same question...check the harness here?  Quite tricky to get to.

Moving down the line I come to a nest of these types of connectors which are quite difficult to pull apart.  I'm trying to be careful and not break any of these.  Any advice on the correct method?

I am having difficulty with these style connectors.  I am able to do a half assed job using emory paper and a tiny flat blade screwdriver, but advice on a better way will be greatly appreciated.  The largest trouble is broken connectors.  I've found two broken ones and broke one myself.  So first, what's the correct removal method so my ham fisted self doesn't break any more, and second are replacements available?

Not related to my task at hand, but I came across this dude.  Is this the dash pot?  Should there be a vacuum line attached here?  I can find no loose hose or apparent corresponding naked nipple.

Last question for this round - what is the recommended method of removing vacuum hoses without tearing them up?  So far most of mine seem pretty new and flexible, but older ones seem fragile.

Did I mention that this is kinda fun?

•  

[siteunseen]

Dashpot is open to atmosphere. No hose. Green and black wires on top of intake are the coolant temp sensor and the thermotine sensor in the thermostat housing. They should be cleaned and lubed with dielectric grease. They're bullet connections and tough. Use two pairs of pliers and pull them apart. Don't grab the wire though just below where it crimps into bullet connections. The snap on clips like the injectors have a flat C looking clip that holds them in place. Use a small screwdriver on one of the sides and pop one side out. Do the other side too. Pull the top with needle nosed pliers until the plastic houseing comes loose. Be careful not to loose the clips. Look on ebay for "280z fuel injection connector kit" and you'll understand better. Those green wires with the bullet connections really need cleaning,  important. Pull the brass sensors from the thermostat housing and shine those up too. You need this. Both less than $10 and would do 4 cars. CRC electronic spray cleaner and any dielectric grease.

 

 

[Captain Obvious]

Your suppositions so far are correct. The device above the ECU is the fuel injection relay, the item below the brake booster is the dropping resistors, and as site already mentioned, the device with the naked nipple is the throttle let-off dashpot. It doesn't get a hose, but there should be a little filter under that white plastic cap.

As for connector cleaning... I've found that the ECU and FI relay are usually OK, but anything in the engine compartment is suspect. However, it never hurts to take a look at any connector just to be sure.

And about the vacuum lines, if they split or crack when you take them off, then it was time to replace them anyway. 

[Zed Head]

Do the resistance and voltage testing at the ECU connector before you get too crazy with cleaning.  After the cleaning, you'll get the satisfaction of knowing you made something better or the agony of knowing that you broke something that was fine.  Both good reasons to have a beer.

[mentalite]

I went ahead and did the testing at the ECU and came up with a couple trouble spots.  It looks like the AFM is toast, but I'd like to verify.  The air temperature sensor is bad with no continuity at the ECM nor the AFM itself.  The manual says that this means replace the entire thing, but is that really the case?  Anyone break the unit open and replace the air temp sensor only?

The flap on the AFM rubs the housing about halfway through it's travel making a nails on chalkboard sound.  Seems like the flap could be filed down a bit, but is this also a certain replacement indicator?  I don't see how the heck this could even happen.

If the AFM is toast due to the temp sensor or the flap, ignore this paragraph.  My resistance readings are off from the stated values in the manual.  It would be nice if they gave a range of values, but not here.  Readings at the ECU and the AFM are close to each other.  Are these acceptable?  I've read a couple other threads describing adjustment to change the resistance.

• Test between pins 6-8 is 228 ohms and should be 180
• Between 7-8 is 255 ohms and should be miniscule
• Between 8-9 is 128 ohms and should be 100

 

Assuming I need to replace the AFM, could I get some advice on replacement options?  I see reman units on ebay for $100.

Oh yeah, today's Name That Component installment.  Three items in one photo.  The little bullet near the coil which has a wire leading to the distributor?  The five sided black box?  The white plug doohickey that has wires going into it, but leads to nowhere.

[Zed Head]

The vane scraping is bad and could cause fueling problems.  Sticking open will make it run rich.  There's a backfire relief valve in the vanes of later model AFM's so the vane doesn't get bent.  It is a thing.  The 228 and 128 aren't terrible.  Not clear the the AFM is worthless although it does need attention.  I'd tweak the vane until it moves freely.  Check the counterweight on the other side also.

The little bullet might be to the condenser/capacitor also shown in your picture.  The 5-sided box is the junction box for the wires from the distributor to the ignition module in the cabin.  If you don't have wires from the distributor there you might have an ignition module modification.  The white doohickey is a test port, for the BCDD I think (Emissions chapter).

[mentalite]

Thanks, Zed.

It sounds like the air temp sensor can be replaced separately.  Sourcing one separately seems to be another issue.  Any good sources for these or the entire AFM?

 

[Captain Obvious]

I've not looked hard, but I'm not aware of anybody selling the air temp sensor separately from the AFM. And I've not heard a lot of people having failures with that component either. So with that in mind... Before you go chasing a replacement are you sure the ATS has a problem?

 

Out in the garage on a cold December day in Harrisburg, your ATS resistance should be up around 5000 Ohms. That high resistance can appear to be open circuit (or "no continuity") to those not expecting it to be that high and not having the meter on a range capable of detecting it. In other words... When you say you have "no continuity", what range is your meter on to make that determination?

 

All that said though, those other AFM measurements don't look so good. Especially the 255 between 7 and 8. Between that and the scraping inside, it makes me wonder if someone hasn't been in there mucking around in the past. If I were you, I would ask around a little on the forum if there is someone who has a spare you can use just to test the system. I'm sorry that I don't have a spare AFM, but I'm sure someone here does.

[Captain Obvious]

For resistance measurements of the temp sensors (both air and water), here's a thread I put together with some detailed info:
http://www.classiczcars.com/topic/56146-280z-efi-temperature-sensor-vs-resistance-chart/

 

[siteunseen]

Whatever you decide to do with your AFM make sure and connect the ground wire on the bottom to one of the mounting bolts.  I've read where a lot of those wires aren't connected and it now they are .

Here's an explanation the flaps get deformed, one way, backfiring through the intake is the main reason though. From atlanticzcars, http://atlanticz.ca/zclub/techtips/afm/sizeupgrade/index.html

 My '77 had a big hole where the EGR tube connected to the intake.  It popped like crazy when I first drove the car if I gave it too much fuel.  

Here you can see the AFM bypass adjustment screw. It is used to close a passage under the primary AFM passage.
This passage is primarily used to vary the air to fuel ratio at idle. The screw controls how much "extra air" bypasses the AFM.
Closing passage is accomplished by turning the screw CW.
btw When the intake "pops" aka front fire usually due to running lean;. the energy passes through this passage. 
If it is closed off, the energy will damage the flap.

 

[Zed Head]

EuroDat had a problem and improvised a fix.  There are also several other manufacturers that used AFM's, like Toyota, BMW, Mercedes (edit- maybe not MB, they used the D-Jet), Volvo.  All licensed the EFI technology from Bosch so probably used very similar parts.

 

Edited January 2, 2017 by Zed Head

[mentalite]

On 1/2/2017 at 11:16 AM, siteunseen said:

Whatever you decide to do with your AFM make sure and connect the ground wire on the bottom to one of the mounting bolts.  I've read where a lot of those wires aren't connected and it now they are .

 

It's funny you say this.  The ground wire that ran from the bottom of the AFM and the mounting bracket was WAY loose.  And there is a rubber gasket under it which doesn't make sense to me.