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Hey, I'm looking for some input here. We have an ITB Volvo 142E, with the D-jetronic fuel injection. THe problem is that the car leans out under load. It starts out in the mid-13s for air-fuel ratio at idle and progressively leans out on the dyno until about 4000 RPM, at which point it won't pull any higher. The sparks appear to be OK, we are using an MSD and it appears to be working correctly. We are using about 29-30 PSI fuel pressure, and about 35 degrees total advance (around 5-6 deg advance at idle.)
We are totally stumped: our conjecture is that maybe the computer isn't getting the signal that the RPMs are increasing and therefore the duty cycle of the injectors doesn't increase? It runs up to high RPM just fine in the garage with no load...
Ideas please!
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My intial cut at troubleshooting this problem would be:
1 - Throttle angle - make sure you're getting WOT at the butterfly
2 - ECU harness connector - clean contacts
3 - Throttle switch & connector - is the ECU being told the engine is at idle when it ain't?
4 - FI trigger contacts & connector - clean/adjust or replace
5 - MPS - unlikely to fail lean IMO, but try another unit just in case (part number is unimportant for this purpose)
This would assume a consistently smooth runup that simply lacks power... no misfires, backfires, etc.
FWIW, I run a LOT more fuel pressure... 37-41 psi. But this detail would obviously not keep the engine from running up to speed under load.
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Eliminate MSD-use stock or Bosch blue coil. D Jetronic VERYsusceptible to RFI and/or ripple in power supply, and hot ignition is totally unneccessary for B20E. Unsuppressed secondary ignition wiring is another no-no w/DJet-you MUST use suppressed wires and rotor, whether using 1Kohm VW beetle style plug terminals w/solid wires, or magnetic suppression wires. Solid core/un resitored wires are NG.
Gary's right: 36psi and check the trigger points. Three common faults: oil or grease on contacts; dryed out/seizing swivel pins; worn down rubbing blocks to the point where they barely open. If you have a junk DJet distributor (from anything-Saab/VW, Opel, etc) 4cyl, cut the upper housing off with a hacksaw. You can now put the trigger points in and check the points gap. You can adjust them by bending the arm with needlenose pliers. Adjust them so they both open equal amts. (Bob Griffith claims that biasing the trigger points adjustments biases the relative fuel deliveries to the injector pairs of the respective trigger points. I never corroborated this). I used to degrease them, lube the swivels, file the contacts, then adj the points so they opened equal amounts (.020"?) good luck, phil
PS-Get rid of that distributor advance! Tac the advance plate to the main plate on each side, set the timing to 33*, and watch how much scatter goes away at 6000!
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I have been running more fuel pressure than you are too. It is dependent on your particular ECU,MAP and injectors. On thing not mentioned is a weak injector. I have had them clog up over the winter when not used. I measure the flow on each of mine at least every spring as part of the pre season prep.
You might want to monitor the fuel pressure during a dyno pull and make sure it's not dropping I put a gauge on the cold start hose.
If you want to borrow my spare ecu, map sensor, or distributor to try please let me know.
Charlie
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Thanks all very much, you have given me several things to check. Charlie knows we have been preparing this car and trying to get it to run for about 3 years.
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problem resolution
So we finally fixed this problem, we've been (semi)successfully racing the car this year. The problem appears to have been electromagnetic interference from the MSD messing with the D-Jetronic injection. Switched to stock ignition, and voila it runs just fine. Damn, what a giant waste of time...
