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Issue 1.) The cold idle is too fast. When it's warm and the fast idle valve closes, the idle is right on. I seem to recall on our old 144 or 142, there was an in-line valve in the cold idle circuit by which I could limit the volume of air that flows through the circuit when the thermal valve is open. Has anybody ever seen such a thing? BTW - I'm not confusing it with the A/C triggered valve that that increases bypass air through that sort of "H" fitting when the A/C clicks on. I plan to reverify that valve is closed when it's not energized. Anyone ever seen that extra adjustable valve?
Issue 2.) The car seems to suffer from fuel drain-back when sitting for a day or two, causing starting issues. I have to cycle the pump several times to get it to catch. Once started, it runs fine (except for fast cold idle). Does the fuel pump have an integral check valve? Oh yeah, I also plan to verify thermal timer/cold start injector function.
Thanks again.
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I put a short length of 5/16" fuel hose inside the hose coming from the valve in the head in my 164E to slow the cold idle. I suggest 1/4" you, put a 2" length in and put a ziptie around it to stop the air going around the outside. I never bothered with the cold start injector, because it's never sub 0°C here, but I would have thought one pump of the gas when being cranked would be enough to replace the colds start injector, caution, very easy to flood the engine pumping the D-Jet throttle switch.
The pressure dropping off quick isn't a serious problem, could be either location. Just turn the key off and on 2 or 3 times to prime it before cranking, maybe try a cleaning product?
The cold start injector is powered directly by a wire from the statrer motor via the thermal timer. It's the same for D & K-Jet.
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69 142S Overdrive + 69 164S Manual
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Item 1 - I think that 'extra valve' you refer to was a feature on the K-jet as I recall. I vaguely recall that it was a large black plastic knob that you could adjust. I think the last year of the 140 series got the Kjet on the B20 engine.
Item 2 - As noted by others, the discharge on the pump has a check valve. If the check valve is leaking you will lose pressure causing slow starts. If you still have the original Bosch pump, the check valve screws into the discharge port of the pump. The Bosch check valves are no longer in production. However, the pump used on the 1979 - 1980 Nissan 280 ZX is a dead ringer for the Bosch 2 port pump. The Nissan pump is still in production and the Nissan check valve might fit the Bosch pump and might be available as a separate item from the Nissan dealers (that is two 'mights' in a row).
As a suggestion, if you unscrew the check valve, you can try rapping it and see if there is any foreign object stuck in the valve which might be holding the check ball open allowing drain back of the fuel. However, the reality is that they do wear out.
Finally, the other source of pressure loss is leaking injectors. Seems to me I recall you were fiddling with your injectors already; but, if you haven't done this, pressurize the system with the injectors pulled out of the holders and watch for leaking fuel at the tips. Should be zero.
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So I did some testing last night....
Fuel pressure at the rail jumps right up to ~29 psi the instant the ignition is turned on and the pump runs. As soon as the pump finishes its 2-second prime, the pressure drops immediately to ~15 psi and holds there quite a while (very slow leak down from 15 to 0 psi). While cranking the starter, the rail pressure remains right up there at 29 psi. So I moved my attention to the cold start injector and thermal timer. It appears the 12v signal reaches the cold start injector while I'm cranking the starter, however it doesn't produce a spray. So I will be looking into a possible clogged cold start injector just like I found on a couple of the regular injectors. This car sat for 18 years with fuel in the system and boy, am I paying the price now! I had the tank cleaned out and flushed the supply and return lines but I still think some crud may have found it's way through. I installed a new filter after having the tank cleaned, but since the filter is downstream of the pump I put another transparent filter in-line between tank and pump. The added filter was trapping some crud but then it fell apart inside so I removed it from the equation. Maybe the electric Bosch pump was pulling more fuel through it than it could handle - anyway I'm currently running the stock configuration of the one metal Bosch filter downstream of the pump.
As for possibly having leaky injectors, I checked for that when I was flow testing the injectors. They don't drip when pressurized.
So I'll get the cold start injector to working again, or replace it, and then see if cold starting improves - I would think it would have to improve.
As for the fast cold idle, I will make darn sure that all the associated hoses in the cold start path are snug and that the A/C air bypass valve is closing tight. I also want to put a timing light on it and make sure the centrifugal advance isn't kicking in too early and making what would have been say a 1000 RPM cold idle into a 2000 RPM idle. I need to find an RPM vs deg of advance chart.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (fixed the ignition - now back to the brakes again)
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I have an extra AC bypass valve I do not need if yours is leaking.
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Antique Swedish Steel 71 142E color V#102
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Hey, I appreciate it. I'll let you know if it's needed.
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Chris;
1. Check for a vacuum leak in that path! I guess there isn't there any sort of fine flow adjustment to the Cold-Start valve Throttle bypass path...when it's cold and open, bypass air, and resulting idle is what you get...I suppose you could add some flow limiting if it's really high, or just partially block hose, but it does sound to me like a possible vac leak...
2. Yes there is a check-Valve in the FuPu and Regulator output is supposed to hold Pressure, but not for days...that 2 second prestart precharge running of the FuPu should be enough time to bring Fuelrail up to operating pressure, if not, perhaps you have a flow restriction or other issue...check you Fuelrail pressure!
Good Hunting!
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Thanks for the suggestions Ron.
1. I had already checked that entire bypass path for loose fitting hoses. One of them that is upstream of the thermal valve is a bit loose, but I figured if it leaked it would be a mute consideration. I will probably put a hose clamp on it just be be thorough. I also want to check the A/C bypass valve just to make sure it's closed.
2. As you suggest I think I'll put a fuel pressure gauge on the rail so that I can see how the pressure rises and also how fast it falls after shut-down. I'm wondering, even though it's a loop system, if the fuel is draining down and pulling air into the rail through the injectors that gets trapped behind a couple injectors until I've cranked the engine enough to bleed it back out. I also need to check the cold start injector function. If it's not working correctly that could be a big part of the problem.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (fixed the ignition - now back to the brakes again)
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Chris;
1. Open upstream of FIC wouldn't affect Idle (it would mean drawing unfiltered air only)...an opening to atmosphere downstream of FIC would allow drawing in false (unfiltered) air and certainly raise Idle.
2. Fuelrail pressure is THE most important thing for D-Jetronic! ...and "fuel is draining down and pulling air into the rail through the injectors" I don't think flow (of ANYTHING...fuel or air) is possible in that direction...think of the pressures...under No conditions is pressure EVER higher in intake than rail...don't overthink this!
Point of note: By careful calling it closed loop...that suggests FI control is closed loop ...only later systems do that with the O2 sensor(s). D-Jet is strictly open loop fuel control...because it doesn't sniff the exhaust, controller has no way of knowing what is really happening!
As far as the fuel supply system, it would be better to call it a circulating system...FuPu and FPReg bring rail to a constant pressure, FI Controller and Injectors control consumption and the volume not used during operation is circulated back to tank...but you knew that...
Cheers
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