Volvo Repair Questions? Ask a Mechanic for Answers ASAP
Hello and thanks for your question. My name is XXXXX XXXXX I will do all I can to help.
Let me first ask, do you have injector pulse when cranking?
You need a noid light, or a 12 volt test light wired between the two pins in the injector harness.
Also, Turn the Key ON, and do not attempt to crank. Does the check engine light come ON in the instrument panel. It should turn ON with key ON and go out when cranking.
Do you have fuel pressure at the rail?
Before we changed out the fuel pressure regulator it did not, and was not getting fuel. When we changed the pressure regulator we have fuel but did not check pressure
Just turning the key ON, should give you 40 psi at the fuel rail.
Do you hear the pump come on briefly for a few seconds when you cut the key to the ON position?
yes, the pump turns on
alright, I feel that it has ample pressure to the fuel rail then.
But, It really needs at least 35 psi,
verified with a fuel pressure gauge , because if it's less than 20 psi , it won't open the injectors. So it's tricky, because you can push the schrader valve and get fuel out, think it's enough, when it really isn't.
Will it run at all?
or just cranks and doesn't even try to run ?
It will run for a few seconds if we put fuel in the throttle body
so it does run with an alternative fuel source.
Here is what I would do first in that case, we know it's firing the plugs, and it's not getting fuel.
Get a noid light, and check for injector pulse when cranking. a noid light plugs directly into the fuel injector harness. and when you crank the engine, the light should blink. it looks like this.
you can do it with a 12 volt test light, but, you have to rig your light in the injector harness with some jumper wires or paper clips, so a noid light is easier.
You just want to make sure the light flickers indicating the injector is getting power and ground. it should blink when cranking.
You can have fuel pressure, but if the injectors aren't pulsing, your not getting any fuel into the combustion chambers. follow me on that?
It's either not got enough fuel pressure, or it's lost injector pulse, one or the other, since it runs when you put fuel in the throttle body.
the battery has been drained, would that have anything to do with it not running after we put fuel in the throttle body? we just did a quick charge on the battery
Yes it could. ECM does need at least 10 volts to work right.
Is the car cranking on it's on now?
If it is, it should have enough voltage ?
Do you have a fuel pressure gauge by chance?
No, we had to rent one
alright, how much pressure do you have at the rail with key on engine off?
Do you still have it? ]
no we don't, but we can rent it again. Could some of the injectors be clogged to where it is getting fuel but not enough
OK, I doubt the injectors are stopped slam up, these are deposit resistant injectors. and the fuel filter is pretty big, so it's going to hold alot of junk before it clogged injectors completely up.
Check for injector pulse when cranking, (since the fuel pressure gauge is not in your posession right now)
You'll need a 12 volt test light or noid light to check for injector pulse.
If it's got injector pulse, then I'm going to lean towards the fuel pump in the tank as being weak or failing, not giving you 35-40 psi at the rail.
If it does NOT have injector pulse, then I would say the ECM is bad. because we know it's got spark, so it should have injector pulse.
I'm leaning towards the fuel pump in the tank,
How do you test the fuel pump with the fuel pressure test kit?
You check for power to the pump, and if it's got power to the pump and no fuel pressure, you know either your pump has failed, or the fuel filter is stopped completely up. I doubt the filter is stopped completely up.
This all wheel drive XC?
yes it is a xc. we tested the pump with the positive, negative charge and fuel shot out of it
Alright, that's a good sign it's got pressure then.
And you hear the pump cut on when you turn the key on correct? it does cycle on for a few seconds?
Alright, with a good charge then, get the fuel pressure gauge back on it, and make sure it's got at least 35 psi with key on engine off, If it's just got 20 psi or so, then it's a weak pump.
Does the check engine light come on with key ON engine OFF?
Alright, then we know the ECM is getting powered up.
What is the ECM
Engine Control Module.
Its located on the passenger side inner fender well. in a block box. It will say Bosch on it. Motronic 4.4
It grounds the injectors, so if you have good fuel pressure, check for injector pulse when cranking, if you don't have injector pulse, then the ECM has most likely failed.
okay and if we have injector pulse what next
you either don't have enough fuel pressure, or you don't have injector pulse. because it runs when you put fuel in the throttle body.
So the fuel pressure would be the fuel pump and the injectors would be the ECM
that is correct.
But you need a gauge to make sure it's at least 35 psi at the fuel rail with key on engine off. if it's 20 psi , thats not gonna work.
So if the pressure at the rail is not at least 20psi at the rail then the pump is bad
no it needs to be 35-40 psi,
What I was saying is , if it is 20 psi, then the pump has failed. you want at least 35 psi.
I believe you'll find your fuel issue there. These ECM's don't usually fail, though I have replaced a few of them. It's not common.
So now we at least have some ideas where to start instead of keep casing our tails.Thank you very much for the information, and if we are having any other issues is there a way to contact you directly through this site
Yes, you can contact me directly when you log in , or ask for me by name in your question heading, also you can rate this chat, it will close this chat, then I click on Questions and Answer format, and then we can continue in the questions and answer format, its just not live chat, but we can do that until you get it resolved.
If you want to do that, that is what I would suggest, I will click into questions and answer format once this chat is closed, and you log off and back in, and you should have an alert queing you to answer me in Q and A format.
Okay, Thanks again Edward
Absolutely, Thank you.