Mitsubishi Lancer Evolution Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter #1
Hi all,

I've got a low fuel pressure problem that started after replacing my engine with a brand new crate engine. I used to run a surge tank with the factory system feeding it but have now reverted back to just using the factory system, connecting the lines as they were from factory.

I've searched and done heaps of diagnosis but have got myself stumped on what to check next. These are the things i've checked so far:

replaced fuel pump relay
checked voltage to pump at idle (8.4v)
changed fuel pumps
checked the fuel cradle for any split hoses
bypassed the factory pump housing filter in case it caused any restriction
made sure the pump to filter housing oring is seated properly and even tried double oring along with factory white plastic collar
disconnected both feed and return lines from tank to engine and blew through them to make sure it wasnt blocked
looked at all the lines whilst car was idling to check for any leaks

I fitted an adjustable FPR to the car so i can see what the fuel pressure is and am able to adjust it so that it is on 3 bar without vacuum line attached. The problem i have is that i am also able to adjust fuel pressure all the way down to 5 psi, which is not normal right? Our cars have always suffered from high pressure problems and from what i have read, unless there is a problem, getting it under 25psi is impossible with the factory system in place.

Any help is greatly appreciated! Thanks in advance.
 

·
Registered
Joined
·
826 Posts
Hi all,

I've got a low fuel pressure problem that started after replacing my engine with a brand new crate engine. I used to run a surge tank with the factory system feeding it but have now reverted back to just using the factory system, connecting the lines as they were from factory.

I've searched and done heaps of diagnosis but have got myself stumped on what to check next. These are the things i've checked so far:

replaced fuel pump relay
checked voltage to pump at idle (8.4v)
changed fuel pumps
checked the fuel cradle for any split hoses
bypassed the factory pump housing filter in case it caused any restriction
made sure the pump to filter housing oring is seated properly and even tried double oring along with factory white plastic collar
disconnected both feed and return lines from tank to engine and blew through them to make sure it wasnt blocked
looked at all the lines whilst car was idling to check for any leaks

I fitted an adjustable FPR to the car so i can see what the fuel pressure is and am able to adjust it so that it is on 3 bar without vacuum line attached. The problem i have is that i am also able to adjust fuel pressure all the way down to 5 psi, which is not normal right? Our cars have always suffered from high pressure problems and from what i have read, unless there is a problem, getting it under 25psi is impossible with the factory system in place.

Any help is greatly appreciated! Thanks in advance.
Either your pump is garbage, or you're bleeding pressure off.

quick test is to block the return line. If the pressure spikes to over 80 PSI, the problem is likely the FPR.

If the pressure doesn't spike, you're bleeding fuel. If you aren't visibly leaking, then check to make sure an injector isn't stuck open, and if that't all good, move to the tank and check the line from the pump to the housing "feed" side. Sometimes they get crimped or split over time when compressed. If all those are okay, then replace the pump. You ran a surge tank, and the in-tank pump needed only to free flow fuel to the surge. So it could of been dying for a long time, but you otherwise never noticed because it delivered adequate fuel flow and volume at relatively ~0 PSI.
 

·
Registered
Joined
·
77 Posts
Hi all,


I fitted an adjustable FPR to the car so i can see what the fuel pressure is and am able to adjust it so that it is on 3 bar without vacuum line attached. The problem i have is that i am also able to adjust fuel pressure all the way down to 5 psi, which is not normal right? Our cars have always suffered from high pressure problems and from what i have read, unless there is a problem, getting it under 25psi is impossible with the factory system in place.
The key word in adjustable FPR is ADJUSTABLE. if you back it all the way off it wont let the system build any pressure, or you can crank it all the way down and build all the pressure your pump can handle. with no vac and the car off you should be able to set the PSI to about 43 and have it stay there for a good while. from what you are describing you dont have any issue at all you just need to set the AFPR to the proper static pressure and then attatch the vac line and you should be golden
 

·
Registered
Joined
·
826 Posts
The key word in adjustable FPR is ADJUSTABLE. if you back it all the way off it wont let the system build any pressure, or you can crank it all the way down and build all the pressure your pump can handle. with no vac and the car off you should be able to set the PSI to about 43 and have it stay there for a good while. from what you are describing you dont have any issue at all you just need to set the AFPR to the proper static pressure and then attatch the vac line and you should be golden
Stock Evo X static pressure is approx 48 psi
 

·
Registered
Joined
·
15 Posts
Discussion Starter #5
Either your pump is garbage, or you're bleeding pressure off.

quick test is to block the return line. If the pressure spikes to over 80 PSI, the problem is likely the FPR.

If the pressure doesn't spike, you're bleeding fuel. If you aren't visibly leaking, then check to make sure an injector isn't stuck open, and if that't all good, move to the tank and check the line from the pump to the housing "feed" side. Sometimes they get crimped or split over time when compressed. If all those are okay, then replace the pump. You ran a surge tank, and the in-tank pump needed only to free flow fuel to the surge. So it could of been dying for a long time, but you otherwise never noticed because it delivered adequate fuel flow and volume at relatively ~0 PSI.
Thanks! I'll give this a go and see which side of the equation the problem stems from.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #6
The key word in adjustable FPR is ADJUSTABLE. if you back it all the way off it wont let the system build any pressure, or you can crank it all the way down and build all the pressure your pump can handle. with no vac and the car off you should be able to set the PSI to about 43 and have it stay there for a good while. from what you are describing you dont have any issue at all you just need to set the AFPR to the proper static pressure and then attatch the vac line and you should be golden
There are so many things in our fuel system causing a restriction that I dont think an adjustable FPR could let it go all the way down to nearly zero pressure.

To add to this, my usual tuner gave me a base map that i loaded on prior to getting the crate motor fitted. the shop that did the engine swap also gave me a tune as they said the map my usual tuner gave me was running very lean. Upon sending my usual tuner the map they did at the shop, he saw that they had to add a lot of fuel, so much so, that there must be an issue with the fuel system and this is what led to this gremlin hunt...
 

·
Registered
Joined
·
77 Posts
Have you actually tried setting the AFPR to the correct static pressure and running your tuners map? I just redid my entire fuel system in my 2011 gsr, including pump, rail, injectors, damper, and AFPR, and yes the AFPR WILL let the system go to zero if its backed all the way off.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #8
Have you actually tried setting the AFPR to the correct static pressure and running your tuners map? I just redid my entire fuel system in my 2011 gsr, including pump, rail, injectors, damper, and AFPR, and yes the AFPR WILL let the system go to zero if its backed all the way off.
thank you very much for confirming that an adjustable FPR will let it drop to zero, as that was something that's been really bothering me because i didnt think it was possible.

i'll try my tuners map and see how it goes.

thanks again!
 
1 - 8 of 8 Posts
Top