Fuel Pressure Is Less and Less the Longer You Drive

[JBQ]

I've converted my Corolla 4AGZE from a supercharger to be a turbo (by using GT2554R ball bearing with "merged collector" style exhaust manifold).

The first 3,000 km, it runs perfect!!!
The spooling is very very fast - even better than the original supercharged state.
I can achieve 1 bar of boost at around 3,000 rpm (with half-pedal).

After my mechanic has changed the clutch plate and a bit air-cond. adjustment, these 2 problems occurs:-
1). the car jerks (as though a fuel cut) at around 0.5-0.6 bar of boost.
2). the fuel pressure is less and less the longer you drive!

The 1st. problem MAYBE due to the boost controller is at fault and I can rectify it only after the 2nd. problem is solved.

Now I cannot rectify the 2nd. problem.

When I first start the car, the fuel pressure is 2.5 kg/cm2. After running the car about 1/2 hour, the fuel pressure reduces to about 1 kg/cm2. If I continue driving further, the fuel pressure reduces further to even 0 kg/cm2 but still idle smoothly but no power to run at higher rpm or at boost.

I hope sifu here can give some advices - Thanks very much.

 

[^pomen_GTR^]

fuelpump faulty???

 

[JBQ]

fuelpump faulty???

I suspect so, but my mechanic says the fuel pump is OK.

 

[xtremeleo]

have u change the fpr lately? what happen if u let the engine cools down, before continuing the drive?

 

[JBQ]

have u change the fpr lately? what happen if u let the engine cools down, before continuing the drive?

Yes, I've changed the adjustable fuel regulator and the mechanic again says it is OK. When the engine is cold (over night), the pressure is normal until the car runs again. I've never tried letting the engine cools down and re-drive. I will try it this afternoon.

 

[xtremeleo]

hmm, what brand of afpr are u using now sir? did the drive feels the same prior to changing dat afpr?

 

[JBQ]

hmm, what brand of afpr are u using now sir? did the drive feels the same prior to changing dat afpr?

It is a SARD - but not sure whether it is a genuine one or not. You're right, it seems that the original OEM one feel smoother. You're a sharp guy.

 

[DanzEterna]

are u using your std fuel pump? its not sufficient, change to walbro 255LPH.

 

[xtremeleo]

It is a SARD - but not sure whether it is a genuine one or not. You're right, it seems that the original OEM one feel smoother. You're a sharp guy.

thank you for the compliment sir, appreciate it :) i'd check dat fpr first, den the fuel pump relay. all u need to do is, increase the fuel pressure and check the response of the pressure, make sure u disconnect the fpr vacuum hose just to rule out vacuum leakage. does it increase? den drop? does it increase with revv?

the fuel pump relay may be at fault jugek, but iam 50-50 on dat sir, so check the obvious source first; the fpr since the problem started happeing when it was changed. please report back asap, tq sir

 

[JBQ]

thank you for the compliment sir, appreciate it :) i'd check dat fpr first, den the fuel pump relay. all u need to do is, increase the fuel pressure and check the response of the pressure, make sure u disconnect the fpr vacuum hose just to rule out vacuum leakage. does it increase? den drop? does it increase with revv?

the fuel pump relay may be at fault jugek, but iam 50-50 on dat sir, so check the obvious source first; the fpr since the problem started happeing when it was changed. please report back asap, tq sir

Dear xtremeleo,

1). Thanks. I will follow your suggestions (may be tomorrow morning - I have to leave now).

Here is my testing result before reading this yours of suggestions.

When I started the car the fuel pressure is 2.5 kg/cm2. After running the engine about 1/2 hour, the fuel pressure dropped to 0.5 kg/cm2. Switched off the engine for 10 minutes, after restart the engine, the fuel pressure climbed up to 2 kg/cm2.

2). Regarding the pump's relay, in fact I'm using 2 ralays in parallel to make sure of its functioning.

3). Please don't call me a sir even though I am 54 now - we all are the forum members. I'm playing with this toy in fact as an experiment i.e. high compression ratio about 9.5:1 (skimmed the head), high boost (1 bar), high ignition timing (plus another 5 deg from the OEM) [all are antagonistic to each other] but with high octane fuel (estimated 102 RON) and a very large intercooler. Being 1.6 liter engine and running about 210-220 km/hr, I managed to get 9 litre / 100 km (no ping, no knocking, no damage for 2 years by now).


Dear DanzEterna,

Regarding your suggestion of changing the fuel pump, I think the flow is enough because I changed to a Supra's 2 years ago (if the mechanic still didn't change it - hope so).

 

[xtremeleo]

jbq, where are u btw? where do u get dat 102ron? running a relay in parallel shud be more then enough power supply to the fuel pump, good mod sir (sorry sir, iam a scout and am working wit air force men, so its a habbit when i talk to people, lol).

*waiting for the test result*

 

[chrissyong]

Dear xtremeleo,

1). Thanks. I will follow your suggestions (may be tomorrow morning - I have to leave now).

Here is my testing result before reading this yours of suggestions.

When I started the car the fuel pressure is 2.5 kg/cm2. After running the engine about 1/2 hour, the fuel pressure dropped to 0.5 kg/cm2. Switched off the engine for 10 minutes, after restart the engine, the fuel pressure climbed up to 2 kg/cm2.

2). Regarding the pump's relay, in fact I'm using 2 ralays in parallel to make sure of its functioning.

3). Please don't call me a sir even though I am 54 now - we all are the forum members. I'm playing with this toy in fact as an experiment i.e. high compression ratio about 9.5:1 (skimmed the head), high boost (1 bar), high ignition timing (plus another 5 deg from the OEM) [all are antagonistic to each other] but with high octane fuel (estimated 102 RON) and a very large intercooler. Being 1.6 liter engine and running about 210-220 km/hr, I managed to get 9 litre / 100 km (no ping, no knocking, no damage for 2 years by now).


Dear DanzEterna,

Regarding your suggestion of changing the fuel pump, I think the flow is enough because I changed to a Supra's 2 years ago (if the mechanic still didn't change it - hope so).

in your case 100% is your fuel pump pressure drop,become weak already,if the fuel pump is work fine like walbro 255 usa liter per hour the fuel pressure must be 3.0 kg or 3.5 kg,if u run hi rev will automatic growing up fuel pressure,if you ride to long time also will lousy and up pressure,please replace your stock fuel pump to usa walbro if u buy china one also useless,cause it work same like stock fuel pump will drop pressure also,good luck

 

[todamax]

most probably,fuel pump faulty..i also got these problem last month,change the fuel pump and problem solve...the pump relay should be no problem,because once the relay is not functioning there will be no fuel supply at all..change to a better fuel pump,no regret

 

[xtremeleo]

even though what u guys are saying about the fuel pump is true, iam more to check the easiest and the least expensive first and work myself to the harder to reach and more expensive parts. dat way, i may able to pin-point the problem accurately while making sure which parts are still in very good condition. dats my way of doing things

 

[JBQ]

jbq, where are u btw? where do u get dat 102ron? running a relay in parallel shud be more then enough power supply to the fuel pump, good mod sir (sorry sir, iam a scout and am working wit air force men, so its a habbit when i talk to people, lol).

*waiting for the test result*

Dear xtremeleo,

Here is the test result (with vacuum line cut off):-

1). The reading of the FPR responses well to both the increase and decrease pressure adjustment.
2). The reading of the FPR does not change at high engine rev (7,000 rpm).

Regarding the 102 RON fuel, I condition the 97 RON fuel with:-
1). Two set of Broquet product is thrown into fuel tank.
2). Very powerful resonanced magnets at the fuel line to further increase the atomization of the fuel.

The rough calculation of getting 102 RON:-
1). When I change from Ron 95 to be RON 97, I have to adjust my Super-ITC +3 deg. timing. So, different in 2 RON (97-95) equals to 3 deg of timimg [this is the base formula for my set-up].
2). After I condition the 97 RON fuel as above (i.e. by using Broquet and resonanced magnet), I have to increase another 8 deg. timing. [this means the RON different is equal to 8x2/3=5.3 RON].
3). Thus, the final RON is 97+5.3=102.3 estimated.

Regarding my place, I think we are neighbour. I'm in Seri Kembangan (Malaysia).



Dear chrissyong and todamax,

I'll take note on your advice.