hey guys, i was a little concerned with my cars long cranking time before she'd fire. i looked into possible causes and decided to check how well my injection setup held pressure. yeah didnt last very long considering i could watch the needle fall from 42 psi. what are the most probable causes of this.? fpr? injectors? rails?

 

Fuel pump's internal check valve.
To narrow it down...prime the pump and pinch off the fuel inlet hose and watch the pressure, if it holds...drop the tank and change the pump (also check out the pulsator above the pump).
If it doesn't hold, prime the pump again and then pinch off the fuel return hose...if it holds, most likely a bad regulator, if it doesn't, leaking injector/s.

 

if you're using a Holley AFPR - it's supposed to do that.

 

I have never heard of that! I had a similar problem but since everything is new and I have no real problems that I have found, it kind of makes sense.

 

Yeah, there was a thread on this a while back, and someone reported in that had checked w/Holley about it. Supposedly a safety feature. Mine does it, and has w/both fuel pumps (old & new).

 

When it does fire, does it chug for a bit? I had the same problem and a few of my injectors were leaking. When it would finally start, it would be slightly flooded until it cleared itself out.

 

Where do you expect him to run the gauge ?

-- Joe

 

Your fuel pump is only supposed to run for few seconds then shut off untill your ecm see's a ref pulse from the dissy. So you can turn on the key and get 42 psi then watch it slowly bleed off, since the pump isn't running. See what your pressure is once the engine is started.

Most tpi ecm's wait for 9 ref pulses before they fire the injectors, which is more than 2 full engine revolution. I can't remeber where I read or saw that info at but I'm sure it's correct. That explains alot of the long cranking time on most vehicles. My buddies car started taking longer to start, and it ended up that his starter was cranking slower and of course it was taking longer to get the 9 ref pulses befor it would start. It wasn't long after he noticed the longer starting times that his starter puked.

How long does it crank, and how does the car act once it's up and running?

 

The same place everyone else does.. the fuel rail.

 

Right, so hes gonna prime the pump and pinch off the inlet hose, which will not allow fuel to goto the rail, intern the gauge won't function..

-- Joe

 

ok it will carnk for about 5 maybe seven seconds or then sometimes like 1 sec? but when it cranks a long time it will take a while then fire and ill get a buff of blue smoke. when i turn the key the pressure jumps to 42 psi right away and then bleeds off very fast ( the most allowable was 1psi/min) which i think is still way to much but mine lost about 4 psi/min then it also while its running, if i stab the pedal the car practically dies then comes to life and takes off. i cant check running pressure because i got the throttle body off right now so ill check that soon

 

Pinching off the inlet hose isolates the injectors (assuming it has already passed the regulator test (closing the return line)), and if the pressure holds in that situation, then the injectors are good, and through process of elimination, it points to the faulty check valve in the pump... Is there where you were going Morley??

Let me check my logic:

1) Pinch off return line and pressurize fuel system, if the pressure is still dropping like before with the return line pinched off, then the regulator isn't causing it.

2) Pressurize fuel system and pinch off inlet line (while the pressure is dropping, or if you can, do it while powering the fuel pump); if the pressure stops falling when you pinch the inlet hose, then the injectors are holding and the last remaining item is the fuel pump check valve..

 

No, if you prime the pump..THEN pinch off the line the pressure will be trapped in the fuel rail...barring injector or regulator leaks.

 

BINGO! That's exactly correct.

 

so when i pinch off the return line what am i eliminating? would that be checking the tank and lines up to the rail for leaks? because i just did the return line test and the pressure dropped like always. so tonight i will check the feed side and if the pressure still drops off it is in the rail itself right? like regulator or injectors? which of these two are more common to leak

 

I did close to the same thing, I just yanked th fuel rail and watched for leaks as I primed the fuel pump. I had a pressure gauge too. Both work. My way just requires more work. This way if it is an injector(s), You will know which one it is.

I just had to remember that Mega Squirt gives a priming pulse and that I had to hot wire the relay so it did not spray.

 

The manual I have for this check has you start by pinching off the pressure line...if the pressure doesn't drop it is the pump check valve or pulsator leaking. If the pressure does drop, you next pinch off the return line, if the pressure doesn't drop, it is the regulator leaking, if it does drop it is an injector. You'd then raise the fuel rails with the injectors still hooked to it and pressurize the system and watch for any drops forming on the injectors to determine which one/s is/are leaking.

 

hey morley thanks for the info you gave me that was the most informitive of the bunch i will go home and check it tonight thatt was very helpfull because it narrows it down exactly to the injector,regulator,or check valve. thatnks again guys sure wish i lived down south so i could drive it!

 

ok i did all the checks and when pinching both the return and the supply it still dropped so thats an injector right? i just took of the plenum and am going to take the rails out but is it possible to leave them still connected to the supply line? because isnt the supply line into the rails metal? i could see if it was rubber hose but metal? also when i pulled of the plenum i smelled the vacuum line running into the regulator and i was told if you smell gas in the vacuum line the regulator is leaking. so could it be a little of both. is there anyway i can test the regulator out of the car?

 

You have to take the fuel rail out as an assembly (disconnect the fuel lines where they attach to hard lines down by the PS pump and remove line bracket bolt).. Once you have the whole thing out, there are some lines that can be removed and o-rings replaced (the ones that connect to the fuel pressure regulator in the back, and the crossover at the front)... The supply line can't be removed from the rail assy.

 

If you remove the bolt at the front of the engine that holds the fuel lines, you'll be able to lif the whole fuel rail up off the engine as an assembly, it will flex at the rubber lines then.