I've couple questions regarding a VR conversion I'm trying to get running, it's had various issues all voltage related that I've found so far What is a rough cranking speed? at the moment I'm getting 130-150 RPM which I think is too slow, but could be enough to start up Anyone know what the injector voltage should be? it does get a 11'ish volt feed whist cranking, but when I measure the voltage across a disconnected injector it's measuring 6-7 volts should it be a 12V injection pulse, or is it ran though a ballist (in the ECU) and it should be less than battery voltage? I'm looking in the bentley book, and all it states is use a VAS tooled LED to see if it flashes! thanks, Crispy
we had very similar issue on our race beetle and vento. Our issue turned out to be that the ECU needed 9 volts to start the car when cranking. the 24v vr6 cranks at 270amps and so we upgraded the battery cables (positive and negative) to 300amp. What ECU are you running as would suspect it maybe ECU not getting current it needs to allow the car to fire. We managed to track issue by using a jump battery in addition to battery on car as this helped maintain the current and the car started hence we needed to improve the cabling. On the vento we found the VAG cabling not up to the job. This was using a KMS ECU and a redtop battery.
it should be 12v at all times. but measure from the injector + to ground, if you measure across the pins you'll see a pulsed signal which is probably why its showing low voltage. what age vr is it, if pre-96 did you remember to fit the proper vr6 109 ecu relay
thanks for that, replacment wire from battery has been on the cars replacment list since it got dropped off with me (battery moved to the boot) I have attached a 2nd battery direct to the starter (via jump leads), but the earth is an issue with most of the engine painted -not started up, but slightly faster on the crank The ECU is a OEM, but same rules apply , need to check the voltage drop on all the earths & lives during cranking Across the pins might be the bump steer, I'm using my Fluke Automotive meter, the measurements are taken fairly quick on the Min/Max grab setting TBH I'd not normally use it. I don't have scope at home yet whats the difference in the relays?, I have no idea which 109 is in there, I can cross ref tomorrow. I seem to get the battery feed on the injector + Thanks for the help chaps
Hi Chris, Cranking speed of the engine should be 2-250rpm, if the battery is 60% charged and can deliver 11.7- 12.5V. You would find the crank VR sensor to output around 800mV in those conditions. If cranking and your injectors show 11 Volts at the supply then to me that is normal as the starter does cause a considerable voltage drop, meaning the battery was most likely in a good state of charge. On these engines, because the fuel pump is not primed, pre crank, it is normal to have a long crank ( up to 2 secs) even with a good battery. If it is too slow you have no chance.
the vr6 one works differently to the 4 cylinder ones, its turned on by the ecu by an earth signal to fusebox pin g1/7, then the ecu is powered by the wire to G1/10. on the 4cyl the ecu relay sends an ign live down G1/7 to the ecu, not sure if the vr6 ecu would like that very much? as i say its only on pre-96 vr6, post-96 dont have any ecu relay. fitting one wouldn't hurt anything but it wont do much either! if you arnt sure on the ecu then post up a part number, but basically if it has an isv its early, if not its late edit: this assumes its a mk3 vr managment! if corrado vr then they all are 'early' type regardless and use an ecu relay edit2: and im not going into all the specific differences between rado, mk3 and early/late, thats toyotec's job
Thanks very much for your replies All very useful, I will be replacing the battery cabling this morning, includingfeed to the fuse box ! I thought the injectors were 12V, thats some voltage drop! may be a runner, or not !
What size cables are you using? Would be a good upgrade to use minimum 4 gauge cable on the earths as they are the most important. Battery>Body. Engine >body. I also replaced alternater>starter motor with 4 gauge and this upped my charging voltages too. Although i have some ICE in mine and i have used 0 gauge for battery earths for standard wiring 4 gauge should be enough.
I've replaced all to 300amp'ish cable battery to starter (0 Guage?), new chassis earth welded in, new cable engine - chassis earth, and 200amp cable feeding the fuse box voltdrops issues seem to be gone, but shes still not starting!! one thing thats bugging me is all I can get via VCDS on the cranking speed is a now than 160rpm battery is on charge overnight & job for morning is checking the crank sensor supply voltages - lets hope thats it Even cross ref'd the starter motor which is right
still a none starter I had a couple hours before breakfast! cranking speed still shows up as 160 via VCDS, I've removed the inlet and removed the injectors found all of them to fire in sequence voltage drop goes down to 11.2 V cranking which is good IMO I'm still not happy with the colour of the spark on a removed plug, and the orginals - I have noticed it doesn't always spark on all 6 plugs with is alarming not sure if it's a ECU (tried on the 2 with the car), the coil pack or the actual crank senor. I have a 1.25 volts out of the ECU on the red wire, being a hall sensor I'm sure a measured a 12V pulse on that one during cranking in two minds of wether its spark related, recorded crank speed or actual mechanical fault ( I did have it running once!)
