Paul Graham ("C46")

Just in from a road trip to/from Butte. About 550 miles with a layover scrounging parts in Missoula. Awesome weather, good roads, few deer. Question for the list, the boost seems to build up to 1.5 really fast, killing the fuel pump, so blazing acceleration was out of the question. It's my son's daily driver so not being able to hammer it should be a good thing. Is this a wastegate going bad? Thanks.

Paul
87 5KQT (253,000 miles and still going strong)

gmbchef

Could be. The urquattro has a built in fuel pump shut off for just such a situation. It will also activate at 4000 rpm if one or more of the various sensors is bad. But...since you stated that it hits 1.5 bar really fast, I would suspect a tear in the diaphragm. At what rpm is it shutting off?
HTH

Paul Graham ("C46")

Good question. In all the times staring at the bar indicator, I've never thought to check the rpms. But, as I've run it up to around 110 mph, 4000 rpm doesn't seem to a limiting factor.

Legal notice: We do have a speed limit in Montana.

Note to legal notice: Our state police only has a total of about 225 officers statewide.

urq20vt

Either one will cause an overboost situation, resulting in fuel pump cutoff.

Assuming that the ECU is not modified, fuel pump cutoff occurs at 1.5 bar on the 5ktq. I am assuming that your ECU is stock.

Checking the WG diagphram is easy. Just pressurize, or pull a vacuum on the top WG connection. If it leaks, the diaphram is bad. If not, look at the line going to the bottom of the WG. These also fail. This line should be replaced with silicone line if at all possible.