Low Fuel Pressure

[xAZxE30x]

Car was running perfectly fine since I bought it last December. Never an issue or hiccup.

one day the pump died. Replaced that and was back to normal immediately. Then slow over the next 2 weeks it would occasionally have warm starting issues after driving around. Would take a few tries to start. That slowly moved to a cold starting issue where I’m at currently. First attempt never starts but second attempt it fires right up.

I tested pressure and it was in the low 30’s but steady so I thought maybe FPR or leaking injectors. Swapped new FPR and Bosch gen 3 injectors and still had the same problem but the car was so much stronger so very happy I did the injectors.

the car still drove fine once started so I have just been living with needing to start it twice. But now as of yesterday it bogs down once I get moving and have to limp it back home.

tested pressure today and it bounces back and forth from 20-30, which is very low but it just keeps bouncing which I’m assuming is my bogging issue.

new parts recently:
fuel pump
injectors
fpr
main relay
fuel filter


if I jump the fuel pump relay I can see hear pump, and it quickly builds pressure but not beyond 30 and then it just bounces around 20-30 before or after starting it’s the same.

what should I be checking next? Maybe CPS or coolant sensor?

[500ke30]

Check the integrity of the wires and connectors going to the pump. Make sure the terminal pin fit is good and make sure you don't have excessive resistance in each circuit (damage wires and corrosion can cause this.)

[digger]

if you don't have the correct pressure (not knowing the engine to comment whether you do but there is atleast some issue at the reading should be steady) then either your measurement are in error or there is an actual problem with the engine ( pump fuel/electrical delivery or chinesium brand, FPR wrong unit or faulty or installed backwards, blockage/leak in feed line or return or flipped feed and return line are some things to consider)

Assuming the vacuum reference line is connected with the 3b FPR engine (m20b25) you should have around 37-39 psi at idle and 43 at wot, the 2.5bar FPR engines (m20b27) about 7 psi less

[xAZxE30x]

if you don't have the correct pressure (not knowing the engine to comment whether you do but there is atleast some issue at the reading should be steady) then either your measurement are in error or there is an actual problem with the engine ( pump fuel/electrical delivery or chinesium brand, FPR wrong unit or faulty or installed backwards, blockage/leak in feed line or return or flipped feed and return line are some things to consider)

Assuming the vacuum reference line is connected with the 3b FPR engine (m20b25) you should have around 37-39 psi at idle and 43 at wot, the 2.5bar FPR engines (m20b27) about 7 psi less

it’s an m20b25 so should be 3 bar.

I’ll try another FPR I have. Both I have are 3bar. One is OEM and one is not. I’ll swap back to the old one though and see if that changes anything.

Prior to swapping the injectors I was getting 30psi at idle so figured it was FPR and then that didn’t change anything. It was a steady holding 30psi.

Now since this bogging problem has sprung up it bounces very quickly from 20-30psi but nothing more. When I jump the relay it will build pressure quickly up to a max of 30psi.

I’ll check I have the lines correct but if I didn’t, would it even start? I’ve always thought if they were swapped you couldn’t even get it started.

when I did the pump the tank looked fine inside but still could have a blockage somewhere. Or maybe a kinked line. All fuel lines looked in good shape but I’ll inspect all of those again.

it’s weird though that up until a few days ago once it started it ran just fine. Now it runs like shit and is just being starved once you start driving.

[xAZxE30x]

Check the integrity of the wires and connectors going to the pump. Make sure the terminal pin fit is good and make sure you don't have excessive resistance in each circuit (damage wires and corrosion can cause this.)

Thanks, will pop the pump cover and look at this today