Chevy Astro and GMC Safari Forum banner
21 - 28 of 28 Posts

Administrator
Common Sense + Critical Thinking
Joined
14,534 Posts
Pretty obvious miracle it died right in front of my house and not on the highway, will accept that one. 馃槀
Damn, hope you bought a lottery ticket that day ;)

Edit: looking at the schematic in van manual. Looks like ECMB goes to fuel pump and fuel/oil pressure switch? Cant see anything else thats running off that fuse.
If you look at the diagram, your ECM/BATT 15amp fuse is powered all the time, those little dots show where the circuits are connected. It's going to the fuel pump relay, the oil pressure switch(and through those two to the pump), prime connector, as well as pins b1 and c16 at the ECM. ECMs rarely fail so very unlikely to be your problem and I agree with Bob that it is most likely a wiring problem. The movement and vibrations from starting/driving could be moving the wires.
I can put a new fuse in and it doesnt blow unless i turn the key. I just tested it and as soon as i turn ignition on SNAP the fuse blows.
If it is only blowing the fuse while starting/running, then it's most likely between the pump and the relay or between pump and pressure switch as those parts of the circuit are only turned on when the relay is engaged while priming and running and once there is oil pressure(~4psi) closing the oil pressure switch.

If it were mine, I would first inspect all of the wiring as well as possible, paying close attention to bends, were it runs close to anything, and where it's supported. If that didn't show anything and I had to drop the tank to inspect the wires, I would go ahead and replace the pump, sock/strainer, filter and get rid of the pulsator that degrades while I was there.
 

Registered
Joined
97 Posts
Discussion Starter · #22 ·
Hey guys!

Discovered some interesting things.

I decided to do a test and see if i could replicate what happened last time i drove it.

Started it up, when back and forth in reverse, and forward. Didnt die.

Put the brake on, gave it a little gas. Same process people do for testing motor mounts. In forward it didnt die, but as soon as i did that in reverse, BAM! Dead.

I took engine cover off and it started up again, did this again while watching the engine flex on the mounts...

In reverse the passenger side of engine moved quite a bit more, to the point where i think that engine mount is broke or bad, causing too much flex on engine which would put a lot more stress on wiring then they were designed for...

I was going to post a video showing what im talking about but havent got it started yet. Will post one as soon as i can. If i have a bad motor mount, which caused this in first place seems obvious i need to fix that first before wiring. But considering how much the engine moved up on passenger side in reverse i can totally see how that could break a wire/wires over time.

Was going to pull the battery today and go over those wires that go through firewall but its pouring down rain so not sure if i want to tackle that. If i open that up and it needs soldering thats a clear day job.
 

Registered
Joined
97 Posts
Discussion Starter · #23 ·
Oh and i just now checked to see if i have spark at the coil and not getting any. Any tips on checking coil? Theres a white and pink wire coming out of it, with key on im getting 12v out of both... the schematic is not too informative what either of those wires are for.

Any idea what the voltages should be on either of those wires?

Schematic Font Material property Parallel Engineering
 

Registered
Joined
97 Posts
Discussion Starter · #24 ·
Also if im correct this is the fuel pump prime connection:
Automotive tire Motor vehicle Tread Synthetic rubber Tire


I have the battery out charging, tested continuity from that prime connector to battery ground post on van, reads 100% continuity. Im thinking aboit it, and that wire you put 12v on it to prime/test fuel pump, so it shouldnt read ground on it. Thinking that may be one of my shorted wires, cause i havent found any others...

But with that engine flexing as much as it is im concerned about more wiring issues than just this. Because right now, getting no coil spark. Red wire going into coil has voltage but could not get it to spark. And van is dying without blowing any fuses so could also point to a broken ground wire too?

Wish i had a shop or a garage sooo bad. Really hard to work on a car in the rain especially electrical stuff.

I feel completely confused at this point and no closer to fixing this sucker than a couple weeks ago but getting more and more familiar with the whole thing and hopefully closer to figuring it out..
 

Registered
Joined
97 Posts
Discussion Starter · #25 ·
Okay thats all i can do today, about to get dark but i found some possible issue spots in wiring harness and discovered that the fuel pump is completely shorted out...

First, that motor mount is completely broken:
Automotive tire Motor vehicle Automotive exterior Gas Vehicle door


At the front and back of the passenger side valve cover, the harness insulation is eaten through.

After finding out the gray prime wire was shorted, i moved to the oil pressure switch plug and tested the gray wire there. That had about 30 ohms to ground. I hooked that up to my meter on continuity mode and turned it on, letting that annoying coninuity beep stay on while i wiggled and inspected the wiring harness from firewall behind battery to fuel pump relay, and inbetween relay to oil pressure switch, and from there all the way to where the wire runs up over the gas tank. None of this broke the continuity. I did find those spots on valve cover that need to be inspected and addressed, but im not convinced theres a short in this circuit there yet.

Then i unplugged the fuel pump connector thats under the van on driver side by transmission. Meter beep went off and the short was gone. Moved my meter from oil pressure switch to that plug and it shows theres a short. So theres definitively a short between that plug under the van and fuel pump. The engine moving couldnt have caused that short, but im not dismissing the idea that the engine moving caused a short that fried fuel pump causing it to short out.

Heres some pics of what i discovered:

This bundle of wires was touching that flexible asbestos pipe that routes exaust into intake manifold. I didnt see any bare wire but will inspect further and get some better heat protection tape on this one...
Finger Wood Automotive tire Tire Human leg


Had to take the oil dipstick out and exaust to air intake hose off to get to this one but can see where wires were up agains corner of valve cover. Inspected with mirror but did not see any bare wires. I think i'd have to remove alternator to get to that to fix if theres an issue there.
Automotive tire Finger Nail Cloud Gas


Oil pressure switch plug where i was getting short to ground on gray wire that feeds fuel pump. Orange wire here and at relay had not short.
Clock Sports equipment Automotive tire Measuring instrument Automotive lighting


Well folks any input always appreciated im going to try and source some engine mounts, and get that taken care of and also mentally prepare myself for dropping the tank or cutting a hole in the floor to access fuel pump.

Also need to find some good wiring harness insulation or whatever its called. Would be sweet to have something that could resist heat going over the engine like that. The corrugated stuff my auto parts store has is super thin and flimsy, even more that what was originally in there, bought some 1/2" but they dont even have any thicker stuff to put over the fat bundle of wiring harness.

Supposedly not suppose to be raining tomorrow, if so would be a good time to go over the wires behind the battery. Dont like having my hood open when its dumping out there.
 

Registered
Joined
1,576 Posts
Ya your motor is jumping all around. First, last time it died, did it blow the fuse??
Now, as far as the way you are testing things, of course you will have continuity on the grey wire to ground, testing it the way you are. The fuel pump is always connected to ground
 

Registered
Joined
97 Posts
Discussion Starter · #27 ·
Ya your motor is jumping all around. First, last time it died, did it blow the fuse??
Now, as far as the way you are testing things, of course you will have continuity on the grey wire to ground, testing it the way you are. The fuel pump is always connected to ground
Last time it died it did not blow any fuses. It hasn't blown a fuse since i got it towed 2 weeks ago.

Thanks for the tip on the testing. Did not think of the continuity going through the pump.
 

Registered
Joined
97 Posts
Discussion Starter · #28 ·
I ordered genuine GM replacement motor mounts, and an off brand cheaper transmission mount. Will be about a week til those come in. But plan on continuing the electrical checking in meantime.
 
21 - 28 of 28 Posts
Top