Well, now my RB20 will idle for about 10 seconds or so, but then my fuel pressure starts dropping out until it dies. Even with some fuel pressure in it, it hesitates when I touch the gas to rev, and bogs out around 1500. Datascan says code 55...all good.
What are the different ways to check for fuel dump causes (before pulling the fuel rail and checking o-rings)??
More specifically: Can a vacuum problem affect the FPR and cause fuel return to open up straight back to the tank? anything like that? I'd like to know for sure that pulling my rail is the right thing before I waste my time.
Also, I can look at an o-ring for obvious damage, but how do I inspect my injectors if I have to pull the rail??
--TJ
How can I test for fuel dump causes??
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s13_240_rb20
- Posts: 539
- Joined: Wed Jan 23, 2008 4:28 am
- Car: 1990 240sx RB20DET
Re: How can I test for fuel dump causes?? (s13_240_rb20)
you put a new fuel filter and pump in?
Re: How can I test for fuel dump causes?? (Kamin)
I'd guess it's a fuel pump problem, maybe the supply voltage/current to the pump is not sufficient or the pump itself is failing.
[ Edit: the 10 second thing sounds like you have a wiring problem to the pump, like the ECU is priming the pump for that initial period but not triggering the relay to keep the pump turned on... ]
Also double check that your fuel lines are hooked up properly, pump hardline to filter to gauge to rail ... from fpr to return hardline. Also as mentioned above replace your fuel filter, that's cheap and easy.
To check your rail, injectors and o-rings, try this.. Unhook both the fuel hoses then make an adapter (barb hose fitting) to fill the feed hose/rail with 30psi of compressed air. This should be lower than your FPR's cracking point. With a leakdown tester (or your fuel pressure gauge) you can check that the rail/injectors will hold 30 psi without any leak from the FPR... Slowly raise your rail pressure to 50psi via your air compressor line regulator, the FPR should open up around 3bar/44psi [and dump left over fuel everywhere].
If the rail and injectors can hold 30-44psi then you probably have a problem with your pump. Otherwise if it starts leaking as soon as you add air pressure, check out the fpr...
To answer your question about a vac leak causing this... Even the biggest vac leak (vac hose to FPR disconnected) will not cause your rail pressure to go screwy. The FPR should hold 44psi of fuel pressure without any vac source applied, if it doesn't then you have a problem with the FPR. Applying vac to the fpr port lowers the opening psi to around 38psi (depends on your idle vac).
[ Edit: the 10 second thing sounds like you have a wiring problem to the pump, like the ECU is priming the pump for that initial period but not triggering the relay to keep the pump turned on... ]
Also double check that your fuel lines are hooked up properly, pump hardline to filter to gauge to rail ... from fpr to return hardline. Also as mentioned above replace your fuel filter, that's cheap and easy.
To check your rail, injectors and o-rings, try this.. Unhook both the fuel hoses then make an adapter (barb hose fitting) to fill the feed hose/rail with 30psi of compressed air. This should be lower than your FPR's cracking point. With a leakdown tester (or your fuel pressure gauge) you can check that the rail/injectors will hold 30 psi without any leak from the FPR... Slowly raise your rail pressure to 50psi via your air compressor line regulator, the FPR should open up around 3bar/44psi [and dump left over fuel everywhere].
If the rail and injectors can hold 30-44psi then you probably have a problem with your pump. Otherwise if it starts leaking as soon as you add air pressure, check out the fpr...
To answer your question about a vac leak causing this... Even the biggest vac leak (vac hose to FPR disconnected) will not cause your rail pressure to go screwy. The FPR should hold 44psi of fuel pressure without any vac source applied, if it doesn't then you have a problem with the FPR. Applying vac to the fpr port lowers the opening psi to around 38psi (depends on your idle vac).
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BoostFab
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Re: How can I test for fuel dump causes?? (s13_240_rb20)
sounds like you have the fuel line backward at the filter and rail.s13_240_rb20 wrote:Well, now my RB20 will idle for about 10 seconds or so, but then my fuel pressure starts dropping out until it dies. Even with some fuel pressure in it, it hesitates when I touch the gas to rev, and bogs out around 1500. Datascan says code 55...all good.
What are the different ways to check for fuel dump causes (before pulling the fuel rail and checking o-rings)??
More specifically: Can a vacuum problem affect the FPR and cause fuel return to open up straight back to the tank? anything like that? I'd like to know for sure that pulling my rail is the right thing before I waste my time.
Also, I can look at an o-ring for obvious damage, but how do I inspect my injectors if I have to pull the rail??
--TJ
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s13_240_rb20
- Posts: 539
- Joined: Wed Jan 23, 2008 4:28 am
- Car: 1990 240sx RB20DET
Re: How can I test for fuel dump causes?? (BoostsFed)
Well, today my car would turn over, but would only attempt to start with starting fluid (then dies). When key turns to ON, fuel pressure primes and holds steady at 37psi (NO dropping). When key is turned to start, it begins to drop. So I have done a couple of tests.....
I checked my voltage to the fuel pump. Based on it's own ground (engine NOT running but attempting to start), the voltage was 9v...seems a little low?? So I unplugged it, applied chassis ground and 12v, and using some spare fuel line, I could see that my fuel flow was still kind of weak.......should I assume that my Bosch 040 pumps stronger as resistance is applied??
OK...as much as that sounds obvious, I finally got brave enough to check my fuel injectors and o-rings. I have unbolted the fuel rail and popped each injector out. All 6 o-rings are in great shape. But now, HOW can I test for an "open injector" without using the compressed air method mentioned above?? I don't have access to compressed air.
It will probably take me a couple of days to piece that back together again...lol But I am already wondering.....can a faulty injector hold steady pressure when the engine is not being cranked???
--TJ
I checked my voltage to the fuel pump. Based on it's own ground (engine NOT running but attempting to start), the voltage was 9v...seems a little low?? So I unplugged it, applied chassis ground and 12v, and using some spare fuel line, I could see that my fuel flow was still kind of weak.......should I assume that my Bosch 040 pumps stronger as resistance is applied??
OK...as much as that sounds obvious, I finally got brave enough to check my fuel injectors and o-rings. I have unbolted the fuel rail and popped each injector out. All 6 o-rings are in great shape. But now, HOW can I test for an "open injector" without using the compressed air method mentioned above?? I don't have access to compressed air.
It will probably take me a couple of days to piece that back together again...lol But I am already wondering.....can a faulty injector hold steady pressure when the engine is not being cranked???
--TJ