Another is it fuel relay or something else post. Fuel pump hose?

[RedBrickCollector]

Occasional hard starting, no stalling experienced.

The worst of it, the engine shook pretty badly, felt like it fired on every other cylinder or something. After that it would start but die.

If I open the door to listen for the pump running and wait til it turns off before I crank, it starts like normal. I think this may be some sort of fuel pressure issue.

Is there a one way/check valve somewhere in the system? I'm leaning towards a failure for something like that, the hose inside the pump assembly, or the pump itself. Is it common enough an issue to warrant pulling out the assembly to check? Could it be just the fuel filter?

I know fuel pump relay is the most common but right now I'm thinking I can rule that out as it was recently tested, pump consistently turns on when the key is turned, turns off after a few seconds and seems to turn on again when I crank, every time.

[Clemens]

I for example never had fuel relay problems, but 2 fuel pumps in one of my 850ies go bad.

[scot850]

As Clemens said, the fuel pumps go bad (check for 43psi at the fuel rail Shraeder valve), you can jumper the relay in the back section of the fuse box at the windshield (you have to remove the 4 x T25 Torx bolts to remove the cover).

Last thing to check is the MAF (Mass Air Flow) sensor at the top of the air pipe from the airbox to the turbo. Disconnect the connector and see if the car starts and runs. Do not run the car this way, this is for checking purposes. If the car starts and now runs then the MAF is dirty or failed. Try cleaning the connector for the wire connector with electrical cleaner and the MAF itself with MAF/Sensor cleaner.

If disconnecting the MAF makes no difference the MAF is not the issue.

Neil.

[RedBrickCollector]

It runs fine once it's started so I think that means I don't need to check the MAF. I don't have a fuel pressure gauge and there are no rentals around here. Would it be worth pulling it out to inspect the pre-filter and the hose, or do I get a pressure gauge?

[abscate]

Is there difference between cold and hot starting? More likely to be the coolant temperature sensor if this is the case

[RedBrickCollector]

Seems to be the same hot or cold (hot test was 5 minutes in a store after getting it up to temp, and then another 1 minute stop to drop something off.)

I checked the ECT and it's missing the harness but resistance values are as expected. Checked with a multimeter and temp gun.

[jreed]

One way I have read about to measure fuel pressure at the rail when you don't have the correct type of gauge is to use a disposable/cheap tire pressure gauge especially if you already have an extra one lying around. It is reported to work OK once so you can get a reading, then you can throw the gauge away.

[RedBrickCollector]

That's an interesting tip. I don't like throwing things away so I think what I'll do is:

Pull the fuel pump assembly since it's basically free, check the strainer and hose (Been wanting to do this to test and clean the float anyway)
Observe
Buy a fuel pressure gauge
Re-cap the fuel pump relay

[abscate]

checked the ECT and it's missing the harness but resistance values are as expected. Checked with a multimeter and temp gun.

Waitm , this needs more explanation

[RedBrickCollector]

Waitm , this needs more explanation

The sensor and harness are spliced together, the connector is missing.

Read the resistance using a multimeter and checked the temperature of the sensor with an IR thermometer. Compared this to a resistance graph for expected resistance.