My '89 5.3 is running but barely. It acts as if it is flooding. Although I know EFI doesn't do that. My question is just where is the EFI main switching relay located? Could it be faulty and sending on/off signals at the wrong time to the wrong cylinder?

Submitted by vgardino@comcast.net on Mon, 12/23/2013 - 14:33

Doug, I do have vacuum at the ECU pipe. Not much but enough to do the job, I think. Right now I've got to get ready for the holidays so I won't get back to the car until later in the week. Merry Christmas, Victor

Submitted by dougdwyer1@com… on Thu, 12/19/2013 - 07:49

Barometric pressure sensor. It's inside the ECU. With the engine running remove the vacuum line to the ECU and see if you have vacuum. If not, make sure the hose is connected at the engine end (at the balance tube at rear of engine)

Check resistance between the pins of the coolant temp sensor with your meter. Here's the resistance range in degress F and kilohms

68 2.5
86 1.7
104 1.2
122 .84
140 .60
158 .435
176 .325
195 .250

Lots of other things to check but you gotta start somewhere

Cheers
DD

PS- why does this appear on every posting?

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Submitted by bonnettoboot@e… on Tue, 12/17/2013 - 08:51

Be careful, it sounds like it is flooding, this wqs common on these cars when a pressure regulator goes bad. Use the engine dipstick to smell the oil for petroleam, then find a mechanic.

Submitted by dougdwyer1@com… on Tue, 12/17/2013 - 01:16

The FI main relay does not control individual injector operation.

A flooding-like symptom could be a number of this: skewed coolant temp sensor, leaky injectors, faulty pressure regulator, shorted injector harness, faulty baro sensor...etc etc

If you have Mareill ignition you might have a bank of cylinders not operating at all....but "flooding" isn't usually the way that problem is described.

Do you have a fuel pressure gauge and volt/ohm meter?

Cheers
DD