1988 2.5L Three Issues in One Video (Page 1/1)
gjgpff APR 01, 12:23 PM
Hi All,
So, the below video is me starting my 1988 2.5L Manual from cold this morning. You'll see three things that bother me:
1) It takes a LONG time to start. It hasn't failed so far, but it is quite a long crank and I'd like to reduce the cold crank time, if I can.

2) It takes a long time for the idle to get down to its minimum, which is about 950 rpm. I didn't want to bore everyone, but it takes about 3 min of street driving before the idle's down to 950.

3) The oil pressure reading is elevated. I first noticed this the first time I changed the oil last year. I got some NOS AC DELCO oil filters, which seemed fine and used one. There are no measurable oil leaks, and over several months the oil pressure came back to a more normal 40-50 range. Right now I have a new (good style) oil pressure gauge installed because the old one started flapping like crazy. I also have another NOS oil filter installed.

Problem's 1 and 2 don't happen when the engine's warm. Might they be related?

A car-guy friend of mine who's witnessed the problem said I should look into the "choke".

https://youtu.be/_oRJHEPksKk

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Geoff Gibbons
1988 4cyl Manual

[This message has been edited by gjgpff (edited 04-01-2021).]

cebix APR 01, 01:05 PM
RPMs sound normal I guess for a cold duke. They like those 2k rpm.

Cranking time... don't know about that.

Oil pressure seems wacky - it shouldn't drop to where it was at the start of the video when the ignition was off. My guess would be the gauge is faulty. Also you have the factory issue with the coolant temp going full high instead of the idiot light going on during the bulb test. That's an easy fix of swapping 2 wires in the cluster and I think the 2 in the sensor in the cylinder head.

EDIT: There is no choke whatsoever on the duke. Only the IAC valve. Maybe you have a vacuum leak causing high rpms?

Another thing came to mind... Do you maybe have a battery disconnect switch?

[This message has been edited by cebix (edited 04-01-2021).]

Patrick APR 01, 01:54 PM

quote
Originally posted by gjgpff:

It takes a LONG time to start. It hasn't failed so far, but it is quite a long crank and I'd like to reduce the cold crank time, if I can.



When you turn the key to ON (not to START), does the fuel pump prime for two seconds?


quote
Originally posted by gjgpff:

A car-guy friend of mine who's witnessed the problem said I should look into the "choke".



Your car-guy friend must be an old codger. No choke on any fuel injected engine.
skywurz APR 01, 02:59 PM
This acts just like my 87/88 duke (88 duke engine in an 87 long story see sig)
Mine takes forever to crank but I have never heard my fuel pump. I tried to fix this with a new relay and cleaning the connections and idk.
The high revs mine typically calms down after a few seconds but some morning its cranky. I punch the throttle and it then levels out.
My oil pressure has done this exact thing. Read wonky ever since i swapped in the 88. I figured because its if different sending unit from the 87. However after some time now once it warms up it seems to act right for me.

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phonedawgz APR 01, 11:22 PM
There are two things that can turn the fuel pump on. One is the relay and it is powered by the ECM. Turn the key to on (only) and the fuel pump should run for two seconds and then turn off. Then just bump the starter. The fuel pump should turn on again and turn off two seconds later. Please record this (radio off) and lets listen for the fuel pump. Then once the engine starts, turn it off and record till the fuel pump turns off.

The second way the fuel pump is turned on is by the oil pressure switch. If you watch your video, the oil pressure comes up and the engine starts. So as Patrick is hinting at, it looks like the fuel pump relay isn't working but the oil pressure switch is.

Record the video and let's see what it looks like.
theogre APR 01, 11:48 PM
1. 87+ L4 and some other engine take a long crank when "cold."
try crank a sec or 2, stop for same, the crank again often starts sooner then just cranking til starts.

2. Is for anti stall. Cold start, try bumping the gas pedal after a few sec.

3. High read on dash gauge is likely wiring or gauge problem.
Can check dash gauge w/ resistors between OP gauge "pin" on sender plug to ground. 0Ω-0 45Ω-1/2 90Ω-full scale
See my Cave, Oil Sensor

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