BOA cosworth losing pressure (?)

[Diogotap]

Hello, I'm Diogo from Portugal

I bought a BOA cosworth to fit in my 74 cortina.. everthing's mounted and functional except for one thing...
When I fire the engine it runs completely normal, but after a while it looses pressure to 1bar (accourding to the fuel pressure gauge)..
The engine works fine if i'm doing 30/40 kmh... but if I press the pedal it just starts to "stall" (?) ,backfiring, like i'ts drowning..

The car is at the mechanic righ now but I know he put a new fuel pump already... Still nothing.
Can it be the injectors?

Please send heeeeeelpppp

[Krikkit]

Is it running the original fuel system? Has it got an FPR in it? I'd be very careful with fuel starvation, running lean can be extremely damaging.

[Diogotap]

yes.. everything's original..

sorry, what's FPR?

[555 Paul]

Diogotap said:

yes.. everything's original..

sorry, what's FPR?

Fuel pressure regulator.

[Diogotap]

Yes, I have one..

Here's what's happening right now...
...When I start the car it works fine and the fuel pressure is good, but after a while the fuel pressure drops to 1 bar..




(this is what the mechanic send me)

[Oldandslow]

Clogged filter?

[stevesingo]

Check for voltage drop at the pump under load.

[Diogotap]

Oldandslow said:

Clogged filter?

I've just ask the mechanic about that.. he said it doesn't have one

[stevieturbo]

Diogotap said:

yes.. everything's original..

sorry, what's FPR?

Everything is not original.

The engine, the car...and the picture of that Sytec FPR...is not original.

So. Has the car ever ran correctly ? Is this a new build/install ?

Explain your entire fuel system ? from tank right through to engine and regulator ( although yes we can see it )

[Oldandslow]

Diogotap said:

Oldandslow said:

Clogged filter?

I've just ask the mechanic about that.. he said it doesn't have one

There should be or you'll clog up something more expensive.

Just below the brake master cylinder there's a stty looking brown thing connected to the fuel pipe going to the shiny, new pressure regulator and gauge. Looks like a filter housing to me.

Ideally there should be a coarse filter before the pick up pump and a fine one in the line to protect the injectors.

Also tanks not venting can be an issue. Does car run better with full tank or near empty.

[stevesingo]

As I understand an EFI fuel system works, is that in all conditions the fuel is pumped to the regulator and excess is returned to tank. The flow rate through the pump at idle is not dissimilar to the fuel flow through the pump at WOT. The difference being at WOT, less is returned to tank.

So, what is the return flow rate and how does that compare to the stock BOA installation value. If it is less than a stock BOA requirement then there is a restriction between pump and regulator, the pump capacity is insufficient, pump voltage too low or the regulator is faulty.

[GreenV8S]

Diogotap said:

I've just ask the mechanic about that.. he said it doesn't have one

The person who installed it without a filter is an idiot, and the mechanic who thought it was OK to run the engine without a filter is also an idiot.

[Mignon]

It's hard to see your setup properly from the photo but you appear to have an old pressure regulator under the brake master cylinder which needs to be removed. Then the fuel line should branch off to the injector rail BEFORE the new regulator and after the new regulator there should be a return line to the fuel tank. This allows the pump to keep pumping at full capacity without stalling or getting overloaded and keeps new cold fuel flowing through the system.

[Diogotap]

stevieturbo said:

Everything is not original.

The engine, the car...and the picture of that Sytec FPR...is not original.

So. Has the car ever ran correctly ? Is this a new build/install ?

Explain your entire fuel system ? from tank right through to engine and regulator ( although yes we can see it )

Yes, but what I meant was the engine itself and it’s parts have no mods.. besides the fuel pump that it’s new and now that pressure regulator.
This is a swap .. the car as never ran perfectly.. first, it would die if I didn’t give it a little gas but responded good if I floor it.. the mechanic thought it was the maf sensor but it was not.. next it started happening the opposite thing, the engine only ran normal until certain rpm ...like40kmh.. and started like dying when I floor it.

Hope you can understand my point.

[Diogotap]

stevesingo said:

As I understand an EFI fuel system works, is that in all conditions the fuel is pumped to the regulator and excess is returned to tank. The flow rate through the pump at idle is not dissimilar to the fuel flow through the pump at WOT. The difference being at WOT, less is returned to tank.

So, what is the return flow rate and how does that compare to the stock BOA installation value. If it is less than a stock BOA requirement then there is a restriction between pump and regulator, the pump capacity is insufficient, pump voltage too low or the regulator is faulty.

I thought the pump was lacking capacity too.. it I asked the mechanic and he said the pump has 8bar which is more than enough...right?

[Diogotap]

Mignon said:

It's hard to see your setup properly from the photo but you appear to have an old pressure regulator under the brake master cylinder which needs to be removed. Then the fuel line should branch off to the injector rail BEFORE the new regulator and after the new regulator there should be a return line to the fuel tank. This allows the pump to keep pumping at full capacity without stalling or getting overloaded and keeps new cold fuel flowing through the system.

I understood everything you said except the “branch off “.. what do you mean?

[Diogotap]

Oldandslow said:

There should be or you'll clog up something more expensive.

Just below the brake master cylinder there's a stty looking brown thing connected to the fuel pipe going to the shiny, new pressure regulator and gauge. Looks like a filter housing to me.

Ideally there should be a coarse filter before the pick up pump and a fine one in the line to protect the injectors.

Also tanks not venting can be an issue. Does car run better with full tank or near empty.

I already told the mechanic and he will take the rusty thing off.
He said that thing should be the original pressure regulator (I’m paying him to learn lol)

[Diogotap]

GreenV8S said:

The person who installed it without a filter is an idiot, and the mechanic who thought it was OK to run the engine without a filter is also an idiot.

I’m with you on that.. I don’t know how he’s still a mechanic

[Mr2Mike]

Diogotap said:

I thought the pump was lacking capacity too.. it I asked the mechanic and he said the pump has 8bar which is more than enough...right?

"Pump capacity" infers a volume flow at a specific pressure, not just a static pressure. Above some flow rate, the maximum achievable pressure drops.

However, since it works ok for a while it's unlikely to be a problem with the pump specifications, which really only leaves the electrical supply to the pump and the pressure regulator. Fuel pumps draw quite a lot of current , so it must be wired with appropriate sized wires and with good connectors to minimise voltage drop.

What is the rusty looking thing under your fuel pressure regulator, which the fuel pipe is connected to?

Also as others have said, a filter is absolutely needed in injection systems. Without it any dirt in the tank will clog up the injectors, and could even cause the fuel pressure regulator to misbehave.

[Diogotap]

Mr2Mike said:

"Pump capacity" infers a volume flow at a specific pressure, not just a static pressure. Above some flow rate, the maximum achievable pressure drops.

However, since it works ok for a while it's unlikely to be a problem with the pump specifications, which really only leaves the electrical supply to the pump and the pressure regulator. Fuel pumps draw quite a lot of current , so it must be wired with appropriate sized wires and with good connectors to minimise voltage drop.

What is the rusty looking thing under your fuel pressure regulator, which the fuel pipe is connected to?

Also as others have said, a filter is absolutely needed in injection systems. Without it any dirt in the tank will clog up the injectors, and could even cause the fuel pressure regulator to misbehave.

I also asked the mechanic what it was and he said (he thinks) it’s the original fuel pressure regulator from the engine..