I drive the car for about half an hour and everything is fine and suddenly the fuel pressure drops about 0.5bar at idle and 1-1.5 bar at acceleration. If I let the car to cool down, everything returns to normal until the next 20-30 minutes of running.
I have changed the fuel pump and the pressure regulator but the problem still exists in exactly the same manner.

I use a 20L fuel cell, Bosch in line fuel pump and Sard fpr.

Any suggestions?

 

fuel pump over heating perhaps?

 

I tried that and when I touch the pump after the problem occurs it seems fairly warm, not too hot.

 

Come on guys, I know you can do better than that. I need your opinions.

 

What year car, stock, or after market ecu ?

Also what pump, and have you checked what current it draws. Is the stock wiring getting hot ?


Mark.

 

The car is competition prepared (tarmac hillclimp) MY99 Type-RA with 2.5L engine and M800 ECU and custom wiring
I will connect a volt meter at the pump tonight and see what happens to the voltage when the problem occurs.

 

I have connected a volt meter directly on the pump and the voltage just drops from 14.2V to 14V during acceleration , which I do not think that this little drop causes the pressure to drop.

Any other ideas?

 

pipe swelling somewhere

 

I use -8AN Aeroquip braided hoses throughout.

 

coil packs? sorry private joke.

I think you are going to have to start pointing the finger at the Sard reg or the vac line to it..

You aren't using Samco vacumm hose to the reg?

 

I have swap the Sard with a new one but still the same problem.
I do use Samco vacum lines.

Cheers

 

the samco vac lines inflat under boost.. especially when hot.. they are too soft imho..

I would be inclined to replace them for that reason alone.. it might also be causing the problem.. although unlikely if pressure is dropping on idle.

Simon

 

Thanks Simon,

I will try that too, I will change the vacum hose to some harder one.

 

Vacum Line to the regulator changed. No difference.
However the problem now occurs always not after 20-30minutes of running.
The fuel pressure flactuates while accelerating progresivly but when I try go full throttle suddenly, the fuel pressure goes down immediately.

 

sounds like fuel pump is tired..

 

what ecu are you running ?

the factory ecus run 33% on idle 99% on wot
perhaps your ecu is feeding a duff relay ? or your wiring is showing volts but not amps if you follow my logic

or else try a different pump and see if the same thing happens
thats what I would do

 

I have changed the pump to a new one, still the same problem.
I use MOTEC M800.
I will check the amp to the pump. It must be 13, isn't it?

Also tonight I will pressurise the fuel sustem with the engine off and give the regulator 1.5bar of boost and I will measure the fuel at the return line in a container to see what Litres/hour do I get.

 

Ok, with the engine off, I started the fuel pump through the Motec and with a tire pump connected with a T to regulator and boost gauge, I gave pressure to the regulator. The fuel pressure was 3.3 bar at 0 boost and gradually increased when I increased the boost pressure. I gave almost 2 bars of boost and the fuel pressure responded normally climbing to 5 bar, no flactuations, not drops. I had the headlights and fan on.

It is driving me crazy.

I have a question though... if the engine cuts off for a reason not related to fuel pressure, say faulty coil, does the fuel pressure drop during the cut off?

Maybe I have to look in other areas other than fuel related components???

 

if it is a very quick misfire for example then no.. it will only drop off when the boost drops off.