[142 Guy]

First off, I can't help you with the D jet controller adjustment screw because I sold my controller to a friend with a P 1800E as a back up for his in case it ever crapped out.

When you mentioned bouncy idle, my initial reaction was incorrectly set throttle switch. My 1971 142 service manual and the D jet Trouble Shooting guide differ slightly in the TPS set up. My service manual says

• release lock nut on throttle stop screw and back screw out 2 turns
• screw in stop screw until it just touches the stop on the throttle valve spindle.
• turn screw in 1/4 to 1/2 turn and tighten lock nut (trouble shooting manual says 1 turn)
• connect continuity tester between terminal 17 and 14 on TPS
• loosen two screws holding the TPS in place and turn switch body clock wise as far as it will go - continuity should read open circuit / infinite ohms
• slowly turn the switch body CCW until the tester reads closed circuit and then turn 1 deg more (1/2 mark on the scale on the upper attaching screw). Tighten the TPS mounting screws.
• insert a 0.02" feeler gauge between the stop screw and the stop on the throttle valve spindle. This should open the throttle slightly and cause the continuity tester to go from closed to open. If not, you need to repeat the adjustment.

Make sure that your throttle cable is well lubricated because a sticking cable can screw this adjustment up.

After the TPS is set up, then you can set idle speed with the idle speed screw. You do this with a hot engine and you need to make sure that the auxiliary air regulator is closed (not leaking any air).

When you replace the injectors you should replace the O ring seals around the pintle (nose of the injector) because they will not reseal if they are more than a couple of years old. I use a little silicone grease to help the injector fit into the seal because they are pretty tight.

Ageing B20E/F intake manifolds can be pretty leaky. Air leaks into the manifold do not screw up the fuel mix; but, they make it impossible to set the idle speed correctly. On my B20E, I hooked up my shop vac in reverse to blow into the intake (clamp or block off the MAP sensor so you don't damage it). I then sprayed with a pump bottle of soapy water to find the leaks (all of them). The last leak I tracked down was around the spindle of the throttle plate.

Black spark plugs seems like a fuel mixture issue. How is your air filter? Check the coolant temperature sensor resistance. If the sensor is out of spec this may cause it to go into permanent enrichment warm up causing fouled spark plugs. Do the same with the intake air temperature sensor, although the errors in the intake air temperature measurement do not have the same drastic effect as the coolant sensor.

Fouled spark plugs can be caused by too much fuel pressure, not a lack of fuel pressure.

Check the wiring on all the sensors. On my 1971, the wiring to the sensors and some of the injectors had become hard and brittle and had broken off in places leading to intermittent shorts and mal operation. I had to cut back the engine fuel injection harness and replace a couple of feet of wire and re terminate the plugs.

I have had the BA injectors on my car since 2015 and have had no issue with them. The Bosch D jet plugs fit in them without issue. If you run out of things to check, remove the 4 injectors from the engine; but, leave them connected to the rail and the electrical connectors. Get 4 cups and put them under the injector tips to catch fuel. Turn the ignition on and let the fuel pump pressurize the system and check for drooling injectors.

If you are suffering from pinging, that seems more like an ignition timing issue. If this is a B20E you need to be running 91 octane fuel (R+M/2). Static ignition timing should be set at 10 deg BTDC. If you still suffer from pinging, try reducing the advance a little bit until it goes away. I find that the B20E is most prone to pinging around 2500 - 3500 RPM and about 3/4 throttle.

Your fuel pressure seems iffy. That might be the pump or it might be a dirty fuel filter or the fuel pressure regulator may be past its best before date. However, as long as your plugs are coming out fouled I would be less worried about a lack of fuel. Fix the spark plug fouling and if they are coming out too white then focus on fuel supply problems.

Have you adjusted your valve lash correctly? Don't try and set idle speed until both the lash and the ignition are correctly set.

 

[142 Guy]

I did not mention, but my distributor was changed to a 123 ignition distributor quite a few years ago. Do you mean under the distributor cap where there is the rotor?

@142 Guy : The Beck and Arnley injectors do not appear to have pintle caps on them. I did use new matching set of seals on them (fat and small one on tip) when installing with a bit of dielectric lubicant. Should I have been moving the pintle caps from the old Bosch injectors?

Don't move the caps over to the BA injectors. The BA injectors are a disc valve style injector. If you look carefully you will see that it has 3 (or is it 5??) little holes in the injector tip. The Bosch is the old style pintle valve and you can see the tip of the valve mechanism sticking out the end of the injector. I suspect that the plastic caps on the end of the Bosch injectors may be to prevent impact damage to the valve mechanism. The Bosch operate just fine without the caps. If you put the Bosch cap on the BA injector you will screw up the spray pattern from the 3 holes.

Interesting note, I flow tested both the Bosch and BA injectors to confirm the BA injectors were suitable replacements. Despite having 3 holes, the spray pattern of the BA injectors appeared identical to that of the Bosch injectors.

 

[142 Guy]

With regard to possible FuPu replacement. Noting that the 3 ports style on the 1971 is NLA. I see most vintage parts sites listing the Bosch #460900 as a replacement (looks like it is from the 240 cars?). Those being 2 ports, what is to be done with the third port hose? Can't seem to find any documentation on the conversion required to the two ports variant.

Those Bosch pumps seem decently priced. I figure it cannot be a bad thing to replace/retire the 51 year old Bosch three port unit...

My original Bosch fuel pump developed a leak in 2015; but, it still pumped fine. Not being keen on self immolation, I decided to replace it which was a painful experience. All of the common replacement in-line pumps require a bunch of plumbing bodges to get them to fit and the Airtex pump that VP Autoparts sold me only lasted about 3 -4 months. While trolling around for another replacement I came across the pump for the 1978 - 83 Nissan 280ZX, part # 17011-P7211

It is pretty much a drop in replacement for the later 2 port Bosch pump. The hose fitting sizes and arrangement and the pump diameter and length are identical to the Bosch pump. The only thing that is different is the wiring terminal arrangement - you can no longer use the original 2 pin plug.

It cost me $280 US in 2015 so it was not inexpensive. It is now significantly more expensive. Check around; but, these guys seem to have the lowest price and I think they are the firm that I purchased from in 2015.
OEM NEW 1978-1982 Nissan 200SX 280Z 280ZX Fuel Pump 17011-P7211 17011-P7211 | QuirkParts

Being a 2 port pump, it has an internal by-pass so you just need to block off the over flow line to the tank.

It is not inexpensive; but, being able to mount it in the stock position with no plumbing bodges was worth the extra money for me. Most of the replacement pumps are smaller diameter pumps and require rubber filler strips to hold the pump in the original bracket and they have problems staying put. The Nissan pump has worked reliably since 2015 and is nice and quiet.

I have heard that Nissan licensed (or copied) the Bosch components for the first fuel injection systems on the 280Z. If you look at the injectors and some of the other components they sure look like D jet so it's not s surprise that the pump is an almost exact fit.

 

[142 Guy]

...and in your picture, the "TPS lower [Idle] contact was not even touching [means the ECU NEVER knew it was at Idle!],

leading to permanent enrichment I assume.(I'm not sure about that, because TPS does not do anything but inform ECU that it is at Idle, AND call for enrichment pulses when moving CCW.

Wow - eagle eyed!

I have never examined the idle control circuit in the D jet controller in detail so I don't know exactly what it does other than the idle hunts if the contact is not closed. From superficial examination, the mixture adjustment screw is non functional when the throttle closed contact is not closed so Dalsim007 could twiddle the knob until the cows come home and there should be no effect on non idle fuel mix. I believe that the setting range of the adjustment screw is limited and can actually go lean or rich. As you imply, I don't think the non operation of the idle contact is the cause of the rich fuel mixture.

On some D jet versions including the 1971 Volvo implementation, the idle contact has a secondary function of fuel cut. If you completely close the throttle and the engine RPM is high the closed contact will cause the controller to initiate a fuel cut until the RPM drops to about 1000 RPM where it resumes fuel delivery. If the idle speed is permanently high (aux air valve problem or manifold air leak) this can get you into the weird area where the controller is shutting fuel off and then turning it back on repeatedly - severe hunting idle. Being an analog device I am sure that the RPM values are variable given component tolerances and ageing drift. However, I believe that the contact has to be closed for this to occur and since it appears that it was always open this should not have been the cause of the 'bouncy idle' originally described by Dalsim007. I believe that this fuel cut feature was deleted from some later controllers so it is a controller thing, not a TPS thing as I kind of implied.

 

[142 Guy]

Definitely adding the voltage measure on the FuPu to the to do list. I did add in a gauge along the cold start valve when I adjusted the fuel pressure last year. With ignition on, but engne off, it stays on 20 psi. Engine on idle, the pressure is a steady 29-30 psi. When playing with the throttle cable, it is mostly steady, but drops to 24-ich range (if only for a split second as I turn the throttle valve). It corrects itself to 30 almost instantly. Are you saying it should not move at all ever, not even for a split second?

There is always a transient period when responding to a change in operating conditions. The fuel pressure regulator has to measure a pressure drop before it 'knows' that it has to correct the pressure. The question is how long is your split second? If you can set up to do Ron's oil pressure gauge style measurement (I have done this) with the gauge duct taped to the front vent cowl, go out and take a spin on the highway and do a full throttle test in 4th gear or over drive at around 3000 RPM. If the pressure stays at 30 psi with the pedal to the metal then the fuel pump is functioning correctly.

If the fuel pressure regulator takes significantly more than a split second to respond to an increase in flow requirements it might be getting old; however, even the relatively new Nissan FPR on my 142 shows fuel pressure transients when operating conditions change.

 

[142 Guy]

Three port fuel pumps are available. I have one of these, 7 years, still running fine.

iRoll Motors Inc.

As noted, those pumps are rebuilt. One of the areas where the Bosch pumps fail is developing a fuel leak around the electrical plug connection. That is where my 3 port developed a failure. With disassembly, it may be possible to seal up that leak; but, I don't know how durable that repair is. The other failure area is the brush / commutator. Brush replacement is doable. Commutator repair can be much iffier unless you are going to the huge expense of unwinding and replacing commutator segments (not for $375 plus core charge). The rolling element pump part of the Bosch pump is probably 'last a century' reliable. If you need original then those rebuilds are the only option.

If you don't need original, consider the pump from the Nissan 1978 - 1983 280ZX. An almost exact fit (electrical terminals are different) for the 2 port Bosch pump which is an easy replacement for the 3 port pump after you cap off the over flow line to the tank. Shop around and you can find a new Nissan pump for the same price as a rebuilt Bosch pump.

If you really, really, really wanted an almost new 3 port pump, I bet you could purchase a Nissan pump and graft the motor on to the 3 port pump head. In 1976 the pump on my 142E died on me. The Volvo repair shop took a new 2 port pump off the shelf, unbolted the pump head from my 3 port and bolted it on to the 2 port pump motor body. It obviously never occurred to them to just install the 2 port pump and block off the over flow line which would have been less work; but, not original.

 

[142 Guy]

Engine and transmission grounds are good. I had replaced the fuel filter 2 years ago (about 5k miles on it) with the proper small filter for 1971 (previous mechanic had used a 1972-73 style big metal filter). Fuel lines and hoses were nice and clean at that time. Fuel tank was replaced also 7-8 years ago by a reproduction one. Can has run every summer since then, and was always winter stored with full tank and stabilizer in it. So I don't think the tank would be an issue on this.

Once ignition and TPS issues are sorted and if issue persist on bucking, I'll reach to Mike Dudek at IRoll. At 325 USD (with core refund), his rebuild 3 port original looks like the best way to go about it. Hopefully snow doesn't set up shop too early this December so I can still run around the street and sort it out before the deep slumber!!!

If the mystery fuel mixture persists, you could consider one of these.

O2 Sensor Exhaust Clamp (innovatemotorsports.com)

Combine it with something like this (AEM and others may sell less expensive versions)

MTX-L PLUS: Digital Wideband Air/Fuel Ratio Gauge Kit (8 Ft.) (innovatemotorsports.com)

and you can fabricate a test arrangement that would allow you to monitor your AFR while you drive and figure out where in the operating range your fuel mixture is going lean. This would give you a better handle on which D jet or engine component you need to focus on. If you dislike the exhaust clamp you could weld a bung into the exhaust pipe. The bung is cheaper and probably more accurate if installed in the down pipe after the merge; but, does require some disassembly to install.

 

[142 Guy]

At 325 USD (with core refund), his rebuild 3 port original looks like the best way to go about it. Hopefully snow doesn't set up shop too early this December so I can still run around the street and sort it out before the deep slumber!!!

I believe that is $425 which turns into $375 after you get the core refund. Add on to that your cost to ship the core back to Iroll and with current shipping costs it is questionable as to whether returning the core is a good value proposition.

This ain't my first (parts replacement) rodeo!

 

[142 Guy]

It is nice that it is running. Part of the experience of new to you vintage car ownership is getting to figure out the weird bits visited on the car by previous owners / mechanics.

If you are going to own a Volvo or any other vintage car with D jet, you really have to learn to do the maintenance work on it yourself because the majority of the mechanics / techs don't have a clue unless they are a known D jet specialist.