Crank no start M30

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jacksonramick
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Joined: Tue Nov 24, 2020 4:12 pm
Car: 1991 Infiniti M30 Convertible

Crank no start M30

Postby jacksonramick » Tue Nov 24, 2020 6:43 pm

I'm trying to fix a 91 m30 convertible that has been sitting in a garage for 10ish years. Rust is minimal from being kept indoors, odometer reads 83k miles. I replaced the fuel pump and filter, oil and filter, and spark plugs. I ended up breaking the distributor cap but got a new one, wires and coil all worked fine. I know I have spark (used an inline spark tester) and used the self diagnosis mode on the ECU which resulted in code 55(no faults detected I think). Will crank but wont catch, using a little starter fluid will make it catch for a second which makes me think the issue is still fuel. If the ECU is saying nothing is wrong, is it something with the injectors or maybe the ECU itself. I could really use the help, I don't have too much experience with older cars like these.


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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Crank no start M30

Postby VStar650CL » Tue Nov 24, 2020 7:38 pm

There's a good chance the whole fuel system is nothing but varnish after sitting that long. You can blow Gumout or SeaFoam through the lines, but chances are you won't save the injectors or pressure regulator without removing and soaking them (if they can be saved at all). Check the bottom of the tank with a flashlight for varnish too. If you see giant brown blobs then you should yank it, put in a gallon of Gumout and shake heck out of it to dissolve and remove the crud.

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Crank no start M30

Postby VStar650CL » Tue Nov 24, 2020 7:51 pm

PS - If you do find a tank full of varnish, wash out your new fuel pump too. Hook the motor to 12V and run it for a few minutes in a pail of Gumout to get rid of any varnish that it picked up.

jacksonramick
Posts: 4
Joined: Tue Nov 24, 2020 4:12 pm
Car: 1991 Infiniti M30 Convertible

Re: Crank no start M30

Postby jacksonramick » Wed Nov 25, 2020 4:00 pm

I just cleaned and soaked the injectors, is there a way I can tell they work before putting everything back bcs that was a real pain in the a**.

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Crank no start M30

Postby VStar650CL » Wed Nov 25, 2020 5:37 pm

You can check them electrically easily enough and if they click the plunger is operating. Just put 12V across them (polarity won't matter). The flow and seals are a different matter, that's a crapshoot.

jacksonramick
Posts: 4
Joined: Tue Nov 24, 2020 4:12 pm
Car: 1991 Infiniti M30 Convertible

Re: Crank no start M30

Postby jacksonramick » Sat Nov 28, 2020 7:42 pm

I know I have spark, compression, timing, air, but I’m still not getting fuel in. Fuel pressure gage jumps up during prime and then drops within a few seconds to 0. So far from what I have read, this could be a leaky injector, bad fuel pressure regulator, or check valve on the pump. I doubt and hope it’s not from the pump considering it’s new, so I could use some help. What can I do to check what’s the issue? I seriously appreciate the help!

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VStar650CL
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2004 Nissan Altima 2.5 S

Re: Crank no start M30

Postby VStar650CL » Sat Nov 28, 2020 8:02 pm

If it's dropping off quickly after the key-on prime then the pump is doing its job but the pressure is leaking down elsewhere. With a new pump the odds of a bad check valve are slim. I don't have ASIST in front of me, but if it's a return type regulator you can test it by blocking the return line and see if the pressure holds. If not then it's probably an injector with a stuck plunger or bad seal.

jacksonramick
Posts: 4
Joined: Tue Nov 24, 2020 4:12 pm
Car: 1991 Infiniti M30 Convertible

Re: Crank no start M30

Postby jacksonramick » Sun Dec 06, 2020 10:52 am

Surprisingly the check valve was bad so got a replacement, however still getting a pressure drop. Just took off the IM again and detached the fuel rail. I sprayed some seafoam in it and attached my air compressor to see if it will hold pressure, which it will. Going around to each injector with 12v will make them spray on que as you would expect for a normal working injector. The pressure regulator works too so now I’m at a lost. I did take the spark plugs off, they are new, and there was so fowling on the tips, consistent with leaking injectors. What else could be causing the pressure drop? This car is becoming a real pain. Thanks again

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VStar650CL
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Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: Crank no start M30

Postby VStar650CL » Sun Dec 06, 2020 11:38 am

Did you check the rail with the injectors in place or just plugged? The only thing I can think is that maybe a side-seal is bad. There are a limited number of places the pressure can go, so you can isolate whether it's from the rail forward or the rail back by putting a piece of flex hose in the circuit at the rail, let the pump pressurize it and then clamp it off. If the rail holds pressure when pinched-off then the problem will be in back, if it doesn't then the problem is at the engine.

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goody90q45
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Re: Crank no start M30

Postby goody90q45 » Wed Jan 27, 2021 1:35 pm

Not sure about the m30 but the G50 has a fuel pump control module that can cause these issues. In the g50, to bypass the FPCU, unplug the connector and run a jumper from the ground in the connector to body ground. If the engine starts it’s a bad FPCU.


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