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Discussion Starter #1
Just wondering if the fuel injectors need a signal other than being plugged in to know when to open & close. I have fuel going through the rail, but the injectors won't spray any fuel. I can crank the engine until the battery almost dies, I pull any plug and they're dry. I've got to be missing something. Any help is appreciated.

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Yes, they need a signal. this is a pulsed fuel injection system. it controlls the amount of fuel delivered to the engine by changing the duration that the fuel injectors are open. the ECU needs several signals to determine the correct fueling. Mass air flow, engine temp, RPM, throttle position... it then calculates the amount of fuel and determines the open time for the injectors. the injectors are usually supplied with constant voltage and the ground is pulsed through the ECU. forst thing to check would be to unplug an injector and see if you have voltage on 1 of the 2 leads. if not you need to figure out why not. if you do then yo need to figure out if you are getting the pulsed ground signal from the ECU. the easiest way to do this is to connect a noid light to the injector lead. I think you can get a set of noid lights from several of the automotive store loaner tool programs.
 

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Discussion Starter #3
Thanks for the reply. I don't have a noid light. What I did was stick a multimeter into the plug for an injector. Cranked the engine no change in voltage. I read in a previous post where someone had a similar issue. They swapped their ecu and it solved the problem. I have a spare ecu from a '92 classic. I'll swap that won't and see if that does the trick. If not, does anyone know of a good starting point to check why there isn't power going to the injectors?

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Just to update.... When I checked the injector plug again using the ground from the battery, both pins are showing 12 volts at the injector plug. I guess my problem is trying to figure out why the injectors are t receiving the "pulse" to telling to spray? I'm bring reminded in the worst way abut the temperament of this **** car... I've got to get this thing running again. Any pointers on where to start checking is greatly appreciated.

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the first thing to check is for voltage reaching the injectors. check for voltage between each of the two injector leads and a known good ground (engine block, chassis ground, neg bat post...) one of the leads should have power. you say "no change in voltage", what was the actual reading? if you where getting ~12 volts then you possibly have a short on the ecu side of the injector harness.


Do you have spark? If not you likely won't get any fuel as the ECU recievs the RPM signal from the ingition system and without RPM you won't get any fuel.
 

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Discussion Starter #6
I've checked for voltage @ injector leads. Both sides register 12.12 volts. I am getting spark. I unscrewed a spark plug, attached the wire to it & cranked the engine. The spark plug has a nice blue spark coming off it. So if I'm getting 12 volts at the injector plug its possible that a have short somewhere in the ecu? If it were a short, swapping ecu's should've made a difference. When trying a different ecu, there's no change. Any other possibilities?
 

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It just occured to me that you will get voltage traveling through the other injectors that are still connected to the wiring harness. disconnect all the injectors and check voltages again.
 

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Discussion Starter #9
Thanks for the info... As requested, I unplugged all the injectors. I don't know if this is normal, but when checking the plugs for voltage, the even bank of injectors register 12 volts on one pin only. Where the odd bank of injectors are registering 12 volts on both pins. Possible break in a wire for the even bank, or is that normal?
 

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I believe the results on the even back are correct and that the error lies on the odd bank. with all the injectors unplugged there should be power coming in on one lead. the other lead goes to the ECU and is a pulsed ground. the ECU grounds the injectors completing the circuit to open the injectors for fuel flow. if you are still getting voltage on both pins on the odd bank it could indicate a short between the hot power wire and one of the injector to ECU ground wires.

A1-1.jpg A1-2.jpg
 

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Discussion Starter #11
Thanks for the diagram. I unplugged all the injectors just to make sure the readings were correct, and they weren't. One of the plugs on the odd bank was still touching which gave the incorrect reading. So both sets of injectors are reading 12 volts on 1 pin with the ignition turned on. I've gone onto to checking ecu pins for specific readings & all tests seems to check out. I'm just not quite certain how to go about checking if either the ecu is sending/receiving a pulse to/from the injectors or if the injectors are receiving the pulse. Is there a reading I can take from ecu or dizzy? Here's a copy of what I was using to reference my checks. If I missed something, please point it out.
Thanks,
http://en.wikipedia.org/wiki/Lucas_14CUX
 

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Discussion Starter #12
image.jpg
Not proud to admit it but this purple wire was the reason my injectors weren't firing. The trucks been sitting for a few years and this wire was loose. Go figure... Thanks for all the help ;-)
 

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Hello there everyone I,m new here. I own a 95 classic SWB. I got the same problem just happened to me last week exactly after heavy rainy night. Went out next morning to start the car, won't fire up only cranks. After that I made the following checks:
1- Power is going to fuel pump & fuel is supplied all the way to the front rail.
2- Spark is present, but with an orange colour note:(I did install new ignition coil, amplifier, whole new distributor, spark plugs & wires, injectors, fuel pump last summer of 2015) got 260,000 miles on mine.
3- All connectors to coil were cleaned, ground to ECM cleaned(underneath coolant tank, battery terminals & wires, ECM plug cleaned and checked the teeth on both sides, new relays for main & fuel pump)
4- Distributor cap was cleaned & dried from moisture in & out.
5- Cleaned the two 6.8k resistors.
6- I did fit two new original O2 sensors a few months ago, so not suspected <----
7- Main relay (black base) clicks once when key in position 4 & again after turning the key off within seconds.
----->(All of the above checks and replacement were made by me according to the manual)<----
What is happening now that the injectors aren't pulsing, but when I spray start fluid the engine fires up until it runs out of starting fluid then shuts down. So where else should I be looking? Thank you.
 

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My problem was solved by replacing the fuel pump. Even though the old pump was pumping fuel making me think that is something else, but there wasn't enough pressure for injectors to spray fuel. Plus check the relief valves next to fuel tank.
 

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My problem was solved by replacing the fuel pump. Even though the old pump was pumping fuel making me think that is something else, but there wasn't enough pressure for injectors to spray fuel. Plus check the relief valves next to fuel tank.
Add to your checklist to measure the fuel pressure, if it's below 30, you most likely have a fuel pump issue.
 

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You don't need to connect to a hose, you connect to the Shrader valve in the fuel rail that is fitted there to allow you to check fuel pressure.
 

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My model didn't come with a shredder valve.
You should have a Schrader if you have a 95. If you look at the engine from the front, it will be on your left, in other words, passenger side for the NAS. In the pic below, it's hard to see, but it's in the yellow circled area. I have a black cap on mine, but you should see the valve stemming from the rail just next to the plenum.
 

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