# Fuel pressure



## mouse53 (Mar 7, 2011)

OK How do I check the fuel pressure on my 91 D21 with 4cyl 5speed standard? I have the pressure check set, but don't see the connector anywhere on the fuel rail.
Hey JP2code I'm also 1madmouse on Infamous Nissan, just looking everywhere.


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## smj999smj (Jan 1, 2006)

There is no connector on the fuel rail. You need a "T" connector to either go in place of the fuel filter or between the fuel filter outlet nipple and the fuel hose. Key "on" static pressure should be around 44-45 PSI and should be around 34-36 PSI with the engine running (regulated pressure).


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## mouse53 (Mar 7, 2011)

Thanks, smj999smj, I did end up using a T where the fuel filter is and did get about 36psi running, so probably not the pump. Used a stethoscope to check the injectors and they are all clicking, so they are working. Now to find why the stutter or miss, it's not the plugs, rotor, or cap, they are new. Going to replace the vacuum lines and the plug wires today. The only code I got was 55 so running out of options.


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## jp2code (Jun 2, 2011)

mouse53 said:


> OK How do I check the fuel pressure on my 91 D21 with 4cyl 5speed standard? I have the pressure check set, but don't see the connector anywhere on the fuel rail.
> Hey JP2code I'm also 1madmouse on Infamous Nissan, just looking everywhere.


I wondered when I saw the username mouse53. I figured there weren't too many mouse fans with Hardbody trucks. lol

But yeah, to get a fuel pressure gauge, you are going to have to figure out a way to splice into what your fuel line.


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## jp2code (Jun 2, 2011)

@smj: Do you think this $10 Spectre Performance kit would work?

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Fits 3/8 inch fuel lines
Specifically for carbureted engines
Mounts under-hood in fuel line
Includes a 0-15 PSI fuel gauge

The 3/8 inch fuel line is what I'm worried about. I don't know what size is on our trucks.


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## mouse53 (Mar 7, 2011)

I just purchased a kit from Harbor Freight that has all the adapters and fittings for about $20.00 Works good too, has a Tee fitting and 2 sizes of hose, includes the clamps too.


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## rogoman (Dec 16, 2004)

mouse53 said:


> Thanks, smj999smj, I did end up using a T where the fuel filter is and did get about 36psi running, so probably not the pump. Used a stethoscope to check the injectors and they are all clicking, so they are working. Now to find why the stutter or miss, it's not the plugs, rotor, or cap, they are new. Going to replace the vacuum lines and the plug wires today. The only code I got was 55 so running out of options.


Several things that could cause misfires:
* Is the misfire occurring on any particular cylinder? What brand of spark plugs are you using? You should be using OEM NGK plugs; other brands such as Champion or Bosch many times cause driveability problems in Nissan engines.
* The cam position sensor that's inside the distributor may be marginal.
* There may be a major intake system vacuum leak. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps. 
* Dirty fuel injector(s). Run some good injection cleaner, like Techron, Redline SL-1 or BG products 44K, through the system; give the cleaner about a week or two to do it's job. 
* If you've just replaced a head gasket or if you have a high mileage vehicles with over 100,000 miles are the most likely to start having engine miss problems (it can be less in some vehicles), then it's advisable to have a compression test performed to rule this out. If you have low compression on one or more cylinders, this could be indicative of a more serious condition that would need to be fixed immediately.


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## jp2code (Jun 2, 2011)

Speaking of additives, I've just been turned on to these Liqui Moly products for Fuel Injection Cleaner and Oil Treatment:

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They will not be arriving until next week, but I am excited to try them (based on the reviews on Amazon). The molybdenum-disulfide is supposed to be fine enough to get into tight spaces, cause ticking lifters or clogged injectors to break free and work like new and work built-up carbon deposits off.


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## mouse53 (Mar 7, 2011)

Well I put the truck back together rack and boxes back on and notice that when the truck sits for a bit it starts flooded or missing which clears up fast. Injector leaking probably because i am smelling gas. I am also running out of patience looking for this thing wrong or that thing leaking, what a fricking pain in the ass. I might just start looking for something that isn't so darn hard to keep running right. I like working on my stuff, but every other month or so is getting old. I got my 93 Chevy Silverado with 40K on it and it has never , in the 138,000 miles I put on it, given me as much grief as these Hardbodys. I mean you get a vibration, be prepared for center bearing, non replaceable u-joints , all different lengths, then if it misses could be any of about 130,000 things or sensors. Seems overly complicated, costly, and here you have to pass smog also every other year. Ok, sorry for the rant but lately its been one thing after another and I know this has no place here so please excuse my going on. I have found that there are about 10 + different brands of injectors all from $38.00 to $200+, that can be a chore just figuring out which brand and what cost times 4 or 6. Very soon you can buy another truck for what all these parts cost, it makes it frustrating. I am going to just park this thing and chill for a day or so. Thanks for all the info, it is appreciated.


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## smj999smj (Jan 1, 2006)

If you are replacing injectors, go to Rockauto.com. Personally, I would go with Autoline remanufactured, which I've used before and have had good results. They're like $36 each, which includes the cost of the core, so even if you don't return the cores for a core refund, they are still cheaper than just about anything else. If you do return it, Rockauto makes it easy by allowing you to printout a discounted shipping label and they'll just deduct the shipping cost off of your core refund. 
Sometimes when you get into Nissan injectors, they will ask you for the color code. Nissan sometimes used different injector spray patterns, identified by a paint dot on the injector body, itself. They had black, blue, green, etc. If you were just replacing one injector, you'd want to get the correct one. If you were replacing a whole set of injectors, which I would recommend doing if you are going to replace any, then it really didn't matter which spray pattern you got as long as they were all the same.


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## mouse53 (Mar 7, 2011)

Thanks again, smj999smj. that was going to be my next question since I will replace all. wasn't sure whether to trust remanufactured or what. I buy from Rockauto and did look there and noticed the Beck/Arnlys where cheap like a closeout. I have a nephew that works for Napa and said he would check for me. If he can't get me a good deal, then Rockauto it will be. I think I have to replace the seats for the injectors and read where those have to come from the dealer because they have the best ones. The fuel pressure was good so I think the fuel regulator is ok. I don't see where there is anything else to cause the problems I am having. I will try injector cleaner and wrote down the brands of cleaners suggested by rogoman, ( the miss is intermittent and I wasn't able to pinpoint one particular cylinder as the one missing). I did use NGK plugs and replaced wires, rotor, and cap. I am smelling raw gas, so I am thinking leaky injectors.

Thanks for all the information, I will let you know how it goes or if I need a stick of Dynomite to see how high it gets when I have had enough, LOL. Just kidding C4 would work better.


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## mouse53 (Mar 7, 2011)

Ok after all the new parts and much scratching of my head , it runs a tiny bit better, but not right. Still have a small miss at take off sometimes and you can feel the at idle it goes back and forth, miss then clear up. I did replace all the injectors with new ones, checked all the sensors and replaced any vacuum lines that looked bad or marginal, set timing at 12 and cleaned the MAFF , new O2 sensor, it was giving fluctuating readings, and intake thermo sensor which wasn't working at all. I know I checked IAC valve and it read right, but maybe should remove and clean. Also have read some about the check valve in the pump not working right, but the pump is new. I think I am about out of ideas here. Before the fuel pump went out this truck ran nice for over 6-7 years, now something isn't right.


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## jp2code (Jun 2, 2011)

It sounds like something is up with the fuel pump. I've never worked on the fuel pump, so I can't give any information.


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## rogoman (Dec 16, 2004)

mouse53 said:


> Ok after all the new parts and much scratching of my head , it runs a tiny bit better, but not right. Still have a small miss at take off sometimes and you can feel the at idle it goes back and forth, miss then clear up. I did replace all the injectors with new ones, checked all the sensors and replaced any vacuum lines that looked bad or marginal, set timing at 12 and cleaned the MAFF , new O2 sensor, it was giving fluctuating readings, and intake thermo sensor which wasn't working at all. I know I checked IAC valve and it read right, but maybe should remove and clean. Also have read some about the check valve in the pump not working right, but the pump is new. I think I am about out of ideas here. Before the fuel pump went out this truck ran nice for over 6-7 years, now something isn't right.


At this point it may be wise to perform a compression check on every cylinder looking for a weak cylinder; compression pressure: standard - 192 psi, minimum - 142 psi, difference limit between cylinders - 14 psi. If you find a cylinder out of spec, a valve may be sticking or seating improperly. You can follow up with a leak-down test to try to pin-point the cause.

Again as I mentioned earlier there may be a major intake system vacuum leak. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.


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