1994-2002 [Subscribe to Daily Digest] |
If the pump runs for 3 seconds at startup, then MAP/ECU etc would seem to be fine.
Unplug the pump and see if you can get that to CEL.
I would want to be careful hot wiring the pump. It should get a bit less than full voltage and might overheat and fry if running for a while.
You may have a leak in the brake booster. This booster stores manifold vacuum. After shutdown, you can pump the brake and it works normal, but after a few strokes, the vacuum is depleted and the brakes become hard to operate. You can observe this on another vehicle then eval on the '99. You can hotwire the pump and not how the petal acts, then shut down pump and engine and stroke the petal and note now the petal feels with multiple pumps.
The non return valve in the VAC line to the manifold may also be defective, and this would then not allow the booster to retain peak vacuum levels induced by the pump and/or manifold. You could remove the brake line from the manifold, put your thumb over the end, then with pump running, the booster will have vacuum and you should not feel any pressure drop on the line blocked by your thumb. After shutting off the pump, listen for hissing some where. The pump also has an in-line check valve. If manifold check valve seems ok, then reconnect and repeat the procedure by running the pump and removing its hose and see if you can detect a pressure drop in that hose from this other check valve.
Check condition of these two VAC line assemblies, interconnect points and seal where connected to the booster with 4543898 gromlet.
This other check valve is in-line and located near the end of the cylinder head and along the upper rad hose. Not shown as separate parts for ether vac hose assembly. The WIS does not show this detail, but the EPC does. The EPC also shows that there is a pressure monitor that the WIS does not discuss that I could see. Thje EPC shows that component but does not show a partnumber, but directs to another page that directs to a non existant page... So I do not know if there is a pressure switch or the MAP does the job. If there is hose to a device on the firewall, this might be a pressure switch, and perhaps this senses pressure in the booster instead of the manofold. So WIS and EPC just create more mysteries some times. I suspect that the EPC has an artifact from a motronic application wherer a MAP did not exist and with the T5, that component is handled in logic.
Found the pressure monitor 4692602, used 1994 - 1998 in B258I engines, so it is indeed an art work bleedover when shown for 1999.
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