no fuel

[james kremer]

1990 trooper lx 2.8 auto
I'm having a problem with fuel delivery. Whats happening is I will drive around for awhile and truck will run fine. Come out of store after about 10 minutes and truck will not start. After letting it sit for a couple of hours it will run again. Once in awhile it will also stall while driving. Fuel pump is good (dropped tank). Power to pump is good (ran extra wires while tank was out so I could check when problem occured again). Ran codes and came up 34, map sensor related. Where is the map sensor and what does it look like? Will this cause it not to start? All relays are good also. If anyone has any suggestions it would be greatly appreciated.

[trooperbc]

mmmmmm....according to the official isuzu online parts catalog
http://www.myisuzuparts.com/
from what i can tell, the ManifoldAbsolutePressure sensor was introduced in 06-1990 andLATER ((as part of the California Emission System,91 model)), but i could be interpreting that wrong. so... do you even have a MAP sensor on yours?

what's your manufacture date, and/or is it a California Emissions vehicle?

the MAP measures the opposite of vacuum --i.e. pressure -- as an input to the computer. if you have fuel injection, here's an illustration from that isuzu parts site. it's Number 56. first thing to check would be the 'vacuum' hose that will go to the intake manifold/common chamber somewhere.

[[[ NOTE: EDIT ADD: THIS ILLUSTRATION DELETED by trooperbc to avoid future confusion because it was the wrong one for this truck. the correct one is in a later post below. //bc ]]]

let us know what you find, and we can go from there. //bc

[james kremer]

I do have a map sensor on my trooper. it is located on the outside of the aircleaner. What I really need to know is if this is what is causing it not to start. I went down to the local parts store, they said it shouldn't be the cause of not getting fuel. Truck turns over great, but no fuel from injectors.
And to answer your Question, no it is not a califonia vehicle. Manufacture date is Nov 89. truck is located in B.C. Canada.
I only paid 1000 for the truck, so hopefully I don't have to spend same amount changing sensors.... Any help? Thanks for replying trooperbc.

[trooperbc]

Originally Posted by james kremer

I do have a map sensor on my trooper. it is located on the outside of the aircleaner.

ok, a little confused because your first post you said

"""Where is the map sensor and what does it look like?"""

anyway, so you must have this one number 215,(for future searchers). and could it keep you from starting, possibly, though doubtful -- but do check to make sure that hose that goes to the throttle body area is connected and intact. but, it shouldn't shut off the injectors.



i would make *sure* that the fuel pump relay is not the fault; that it is working properly during cranking; simply swap it out with the exact same relay from a different system.

next, i know on my 1992 trooper (different engine), the fuel pump will not operate unless the computer gets a valid ignition signal from the ignition module. So...at the very least make sure all those wires are connected and functional. i assume you've checked that you have spark at the spark plug wire connectors.


now maybe someone with your engine will chime in...

//bc

[james kremer]

I was'nt sure what the map sensor was, so I went too the parts store and asked for him too pull one down for me. The picture you posted is the engine in my truck. Relays have been swapped already and are not the problem.
I will have to wait untill it won't start again to see if there is spark, but when I had the problem, I looked down the carb and there was no fuel. Has new coil,plugs and wires. Fuel filter is also new.
What is the box that sits beside the coil with two vacuum lines running into it? Seems when I played with the connector running into it, the truck started.(or it was one of the times it just felt like starting).
This is a awsome little truck that I was'nt even planning on keeping, but if I can figure this out, it will be my daily driver.

[james kremer]

And seeing as how you have axcess to these engine layouts, can you please point out the ignition module. THANKS.

[trooperbc]

Originally Posted by james kremer

And seeing as how you have axcess to these engine layouts, can you please point out the ignition module. THANKS.

my access is that new isuzu parts site i pointed out in my first post
http://www.myisuzuparts.com/
go there and have fun, because in some ways its better than a haynes or chiltons manual.
btw, for factory service manuals, not cheap but very good they are at www.helminc.com

for a one year subscription that uses the same info, for only $25 the first year, www.alldata.com

good luck, by using the isuzuparts site and someone chiming in that has your engine, you will get it figured out


//bc

[james kremer]

Well it happened again. Truck stalled while driving. Will not restart. Checked for fuel, none. Checked for spark, lots.
Any more ideas anyone??? I'm completly stumped here!!!
On my way right now to see if it will restart. Sitting at 7-11 and will probably get broken into!

[atfdmike]

Hi, your MAP sensor could definitely be the problem. It tells the computer the amount of air moving through the air plenum and the computer adjusts the fuel to match air flow. You could have a case where if the MAP is not working or connection is bad that the computer is not seeing air flow and therefore not telling injectors to supply fuel. I am not familiar with your model, but there is usually a default mode in the computer that will allow you to limp a while with a bad MAP on newer vehicles. Wish I could be more help. Generally you do NOT want to spray carb cleaner or blow a lot of air through the sensor, as it is very sensitive to damage. Here is some info. good lluck.1990 Isuzu Truck Trooper II V6-2827cc 2.8L

Vehicle Level Powertrain Management Computers and Control Systems Manifold Pressure/Vacuum Sensor Testing and Inspection Testing and InspectionMAP SENSOR OUTPUT CHECK

DIAGNOSTIC CHART
MAP Output Diagnostic Chart

TEST DESCRIPTION
MAP Output Test Description

[trooperbc]

Originally Posted by atfdmike

Hi, your MAP sensor could definitely be the problem. It tells the computer the amount of air moving through the air plenum and the computer adjusts the fuel to match air flow.

for the record, atfdmike, you have mixed up here MAP manifold absolute pressure sensor with MAF manifold air flow sensor, which i don't think he has. two completely different things as your good alldata info explains it.
btw, thanks for posting these very complete and informative stuff from alldata.

//bc

[atfdmike]

Ouch! Thanks for keeping me honest! I have got to slow down when I read the posts. Hope it did not cause any further complications to getting the problem sorted out.

MAP


The Manifold Absolute Pressure (MAP) Sensor measures the changes in intake manifold pressure resulting from engine load and speed changes, converting this to an ECM voltage input signal.

A closed throttle on deceleration produces a relatively low MAP output, while wide open throttle produces a high output. This high output is produced because the pressure inside the manifold is the same as outside the manifold, resulting in a measurement of 100% of outside air pressure.

Manifold absolute pressure is the OPPOSITE of engine manifold vacuum. When manifold pressure is high, vacuum is low. The MAP sensor also measures barometric pressure under certain conditions, enabling the ECM to made adjustments for altitude changes.

The ECM sends a 5V reference signal to the MAP sensor. As manifold pressure changes, the electrical resistance of the sensor also changes, allowing the ECM to "know" manifold pressure. High pressure (low vacuum and high voltage) requires more fuel. Low pressure (high vacuum and low voltage) requires less fuel.

The ECM uses the MAP sensor input signal in its calculations for fuel delivery and ignition timing.

By the way, the ignition module is in the distributor for the trooper II V6 . BTW, I have had a couple vehicles over the years exhibit intermittent starting and running problems due to a bad module, usually only after they warm up and the engine is hot. Best of luck.

[james kremer]

Thanks for replying guys.
The truck will always start when cold, so maybe I will take your advice and change the ignition module and the map sensor as well. While I'm at it I will also change the fuel filter one more time(can't hurt).
Is the ignition module hard to change? And can you also tell me what that box is beside the distributer. It has two vacuum lines running into it,one from the egr and one to the carb.

[atfdmike]

1990 Isuzu Truck Trooper II V6-2827cc 2.8L

Vehicle Level Powertrain Management Tune-up and Engine Performance Checks Distributor Service and Repair Distributor Service Distributor Service Fig. 11 Exploded View Of Distributor Assembly


1990 Isuzu Truck Trooper II V6-2827cc 2.8L

Vehicle Level Powertrain Management Emission Control Systems EGR Control Solenoid Locations Locations Engine Compartment Component Locations.
Top RH Rear Of Engine

Applicable to: 1990 Models w/2.8L V6 Engine

[trooperbc]

Originally Posted by james kremer

....
The truck will always start when cold, ....

have you checked the water temperature/thermo sensor. it seems i've been reading here or other sites about this being fairly common and critical on these engines.

but again, i'm not familiar enough to lead you there on this engine...

//bc

[james kremer]

Well I don't think is it the temp sensor because it decided not to start when cold today.
I went out and got the map sensor and the ignition module today.$161.00. Will post again when installed. Anymore suggestions?
Maybe the fuel pressure regulator ??