Caveman Bosch fuel injection tech info?

George's Cosworth Vega has been molested by a couple of different repair shops, for instance the TPS is way out of whack. It appears to have a variation of a Bosch D-Jet system, similar to an early 914, basically caveman fuel injection (it doesn't use an O2 or lambda sensor, for instance, it operates in open loop all the time). I have Googled my azz off trying to find specs for things like TPS adjustment, sensor resistance values and test procedures etc and have so far come up empty handed, unless you count all the air cooled engine sites. I did find one really decent site for the MAP sensor but it doesn't cover anything else. The CVOA Web site shows where all the various bits n' pieces are but has very little additional info. Anybody got any ideas?

Is there a factory service manual in existence? They're usually the best place to start for troubleshooting, diagnostics, schematics, torques, adjustments, etc.

Bryce

Opel systems were very similar to the set-up in 914's. They are "L" jetronics. Let me dig trough my manuals for some Vega ones and compare and I'll get back to you.

If it is L-Jetronic, I may be able to help since it's the same as used on the Datsun Z cars from 1975 to 1983 and I've fought with them on a regular basis... I believe the BMW's from the late 70's and early 80's used Bosch L-Jetronic as well. The Z/ZX drivers would use the larger BMW 5 series AFM to "cheat" in SCCA auto-x back in the 80's. Externally, it's dimensionally the same, but has a larger "throat" so you could pass more air then play with the fuel enrichment to get a little more oomph out of the "stock" L6. They are extremely simple compared to modern fuel injection systems.

The Bentley Bosch Fuel Injection & Engine Management manual has a whole section of troubleshooting and procedures.

Got a Barnes & Noble bookstore near you? Well work the visit to peruse the fuel injection manuals. The mentioned Bentley Bosch manual is very good, and I think it's Haynes that has a surprisingly good one as well.

The books are pretty useless. If it has a flapper, it is L jet if it has a Manifold Pressure Sensor it is D Jet. Check out any 914 web site, those guys can help. I know D Jet pretty well. You can email me with any questions. Basically the biggest problems are MPS, vacuum leaks and broken wires. For what it is the Djet system works really well when set up.

Something tells me it's actually K-Jet... that's the one with the big flapper. VW called it CIS, but it's the same thing. That's what all the 70s/early 80s BMWs used.

Basically, there's no electronics to speak of in K-jet. There's no timing, no pulses, no duration, nothing. It dribbles all the time. Later variants added some basic elelctronics, but nothing much.

Anyways, with K-Jet,the number one killer is vacuum leaks. Vacuum leaks can make it run poorly, or not at all.

If it turns out it is K-Jet, send me a message. I have some notes tucked away somewehere.

time for megasquirt?

I'm going to check Barnes and Noble, good suggestion.

This one has MPS but not a mass air flow (flap) which indicates a D Jet type system. The K Jet/CIS had the mechanical injectors, this one has electronic injectors. IIRC, L Jet is the electronic flapper (MAF) type system.

The car was in storage for quite a while, a shop replaced a fuel pump and a set of used injectors. It was hard to start and hesitated off the bottom but otherwise ran well. One injector was leaking, so I replaced all the seals; injector leak is fixed. I had to wait forever to get a chance to replace the water pump and timing belt, got it all together and it was still sorta hard to start and hesitated. Somebody's been fiddling with the TPS which appears to have three different circuits inside it. So I need to find out how to adjust it, the CVOA Web site has -zero- information on this.

Anyway, I warmed it up to operating temp, it ran and idled good except for the aforementioned hesitation. Then suddenly, like flipping a switch, it started running stanky rich and didn't want to idle. Unplug the MPS wires, it dies instantly. Pinch off vacuum to the MPS, it runs even worse but continues to run. Pull the MPS hose off the intake, it starts idling high and runs a lot better but is still stanky rich. If I turn the TPS, the engine runs differently but not correctly. This seems to indicate the ECM is taking inputs and changing outputs accordingly, like it's OK. Block off the air intake and the engine dies almost immediately, indicating no vacuum leaks. Parts are not real readily available plus they are sorta pricey, so I don't want to just start tossing parts at this thing.

It can certainly be Megasquirted, but that means adding an O2 sensor, late style GM TPS and a MAP sensor. I'd like to get this D Jet whipped into shape, if possible.

The flapper door style is a VAM (Vane air meter) if it has a sampling tube it is a MAF (Mass air flow).

Verify that the coolant temp sensor is functioning properly, if a spare one is available then swap it out to see if it makes a difference. (Early Bosch units seem to be hyper sensative to bad coolant temp sensors)

That's mostly KE and L Jetronic that's uber sensitive to a bad coolant temp sensor. I don't know about the Vega, but most D Jetronic systems don't even have a coolant temp sensor. I have no idea if they will interchange, but if you need one, I have a few extra TPSs from '68-'73 VW Type 3s with D-Jet.

MPS is crucial. It must have vacuum and there are 2 coils in the thing. Check it for vacuum leaks. I will try to find the resistance values. It also needs a trigger signal, usually from the distributor, a set of points below it. Injectors fire in pairs. Ignore the TPS for now, it will run without it. There are switches for idle, full throttle and a series of on/off signals as the throttle is advanced. Works as an accelerator pump. All you really need for Djet is 12V to the brain and good grounds. MPS working Fuel Pump working Trigger signals from dist. Adjusting FP sets lean/rich BTW.

Found my Djet guide MPS resistance is 90 and 350 ohms

Email me at guthriehill@aoldotcom and I will send a scanned copy of the guide. It is excellent, helped me save a bunch of 914s

Thanks, 16v and porschenut.

This one has both a coolant and intake air temp sensor. IIRC, some of the later 914's had a head temp sensor that served a similar purpose.

Sorry forgot that one. Coolant temp sensor has to be hooked up also. Air sensor will adjust mixture slightly, but on or off the engine should run. Another big problem on start up of Djet is getting enough fuel pressure into the system. Try hot wiring the pump for a few minutes to get the pressure up to 30's

djet is a really good basic system. Take care of the basics and it will work.

There's an interesting site about D-Jets that I bookmarked a while ago:

http://members.rennlist.com/pbanders/ecu.htm

The CVOA Web site has a bit more info which has helped (it would be even better if the login procedure made any sense). Anyway, tested the MPS, it holds vacuum and has the right resistances, the IAT is damn near inacessible (thanks, Cosworth). The pressure regulator holds vacuum as it should, but if the coolant temp sensor is unplugged it runs a LOT better. So I need to pull and bench test it, it has to be done with a voltage (not resistance) test. All indications are that it is toast, wonder where I will find one? The CVOA cross ref shows 'discontinued'. Wonder why?

If it is an L-Jet system, here's a write-up that will help.

I just spent basically the entire spring debugging my Alfa's L-Jetronic FI. Instructions on TPS adjustment, expected hot/cold resistances for many of the sensors, etc.

Big lesson learned, though: CHECK YOUR GROUNDS!!

http://www.hiperformancestore.com/Ljetronic.htm