for the Lh 86 volvo 240 ecu? this fuse goes from power to the main relay? thanks

 

25A. I'm quite sure I mentioned that several times. this is powering the ECU, injectors, idle control valve, MAF, o2 sensor heater, and fuel pumps.

 

Hey Pierce, have you ever notice that red wire that's coming from the 25A fuse getting sheered? Not the one coming from the battery but the one coming from the fuse to the ECU.

I've found 2 completely different harnesses, an 85 244 and an 87 244, both had a sheer in that wire causing shorts with the frame. The sheer itself looks professional, as if someone actually cut off the rubber. It's quite hidden too, so hidden it would be impossible for a human to do it, as it butts against the chassis perfectly. I don't know where I put them or I'd take a pic to show you.


But yeh, OP make sure that wire doesn't have a sheer in it, or that fuse will continue to pop.

 

Changed relays , got 12volt to the fuse and relay ( big red wire, ) but the fuse blows during cranking any ideas? and a note. Bosch lh fuel injection 2.2 is not volvo only Saabs and Audi used the same system so having it on my alfa Romeo spider should not make any difference . lots of bmw folks stuff it there 2002 cars

 

you connected something wrong. how could you possibly expect us to know what you did? we haven't seen your car or your wiring.



edit: p.s. I merged all these assorted threads as they are all dealing with the exact same thing.

 

what sort of fuel pump(s) are you using? how are they being powered ? The volvo used two fuel pumps, a low pressure in-tank transfer pump, and a high pressure main pump under the car... both were powered off the yellow-red wire off your '4-wire' connector. you can actually replace all of this with a single in-tank high pressure pump from a later volvo or similar LH car, such as a Volvo 850

the LH 2.2 fuel pressure regulator maintains about 36 PSI relative to manifold vacuum, so you need a main pump that can maintain somewhat over 36psi while delivering sufficient fuel for the engine at full boil (wide open throttle near red line).

do note, that while many other cars use Bosch LH 2.2, the ECU's are programmed for the specific motor and its fuel-air requirements at the range of RPMs and throttle loads. I'm guessing the alfa motor is somewhat smaller than 2.3L and probably has a somewhat higher redline.

 

It was running perfectly infill a few days ago allways started and ran even the mpg went up.very happy with it, then a few days ago o stopped at the store got back in no start . if you look at the volvo ,1986'schematic you will notice that the entire Lh jet has a small separate harmed, I am not underestimated the knowledge here, yes the alfa motor has a higher red line, I have hit the stock fuel cutoff but on as rolling road to test the mixture ratio and it was great. I will remove the harness from the car and cut it open to check for problems, as it was driving great until a few days ago

 

the fuel pump is off a separate system so less load on the 25amp fuse

 

so what tells your fuel pump when to turn on? normally, in LH, the ECU does it based on the engine turning over, so the pump isn't running when the engine isn't running. you asked earlier about that yellow-red wire and suggested that you'd connected it to ignition, which is wrong.

 

'harmed' ?

translate, please.

 

"harness" sorry ,typing on smartphone,wants to change my spelling sometimes

 

remove the harness,takes only a few minutes,will disassemble the cover to the harness to check for any damage or shorts or bad soldering joints

 

seams to me I have been taken as fool,hum. ,try these sites. ....... Google....efi upgrade to Bosch Lh 2.2 (from volvo )- bmw 2002 faq....... or k jet to megasquirt...' look at a few lines down and you will see in the turbo bricks section of k-jet user's to Lh2.2 conversion

 

ok, took out the harness,removed the covering to check for any broken wire's or bad solder joints,none, next checked continuity of each wire from plug (sensor) to main sci plug ,no problems. I am thinking bad ground to the motor. what cconfusing I'd that I can set the key to run for 5minutes,and fuse is ok, but as soon as I start the car,the fuse blows still thinking bad of loose ground causing the fuse to blow,an

 

any thoughts about this , right track? thanks

 

a loose ground is very unlikely to blow a fuse.

blowing a fuse usually means a 'hot' wire is touching ground. the only circuits that are powered when the car is cranking/running and unpowered when its turned on but not running are the yellow-red wire circuits, which include

• fuel pumps (but you said yours are powered externally)
• injectors
• idle air valve (this uses a brown wire thats connected to the yellow-reds at a junction in the harness)
• O2 sensor heater

with car switched off, unplug your fuel pump relay, and hook up a multimeter in "OHMS" mode between chassis ground and fuel pump relay socket pin 87/2 (yellow-red wire). if you see 0.5 ohms or less, you probably have a problem. 0 ohms would be a hard short. unplug the idle air valve, repeat same test. plug that back in, unplug the o2 sensor, measure ohms again. do this for each injector, too.

what did you connect that yellow-red wire on the 4-pin plug off the ECU to? it should be no-connection, since your fuel pumps are being powered elsewhere (OR you should hook your fuel pump(s) up here instead, the way they are meant to be).

 

I only changed the harness from the o2 sensor to the connections on the motor,from the ecu plug the the o2sensor plug I did not touch,can I do the fuel pump relay to the ground off the car,examples, fuel pump -red/yellow wire to the harness ground?

 

on the 4pin connector ,not plugged into anything

 

I thought about hooking up the fuel pump as the schematic has it ,but the car was running for a year this way,so I do not believe that is the problem

 

ok , checked all connections red/yellow all are connected, no issues , from relay to 4 pin,fuel injectors,idle stability,and + to the o2 sensor hot