AHU no start, can't bleed Injection pump

lugnutgmc

Well-known member
Joined
Apr 12, 2013
Location
Rhode Island
TDI
Working on TDI swap into Mk1
This is for an AHU motor swapped into an 81 Caddy. The motor was running about a year ago in the swap, then I had a valve stick and had to pull the motor to rebuild it and the head. I reinstalled it in the last week, but have not been able to get it started. It cranks great, but I don't think I'm getting any fuel into the cylinders. No smoke or even a hint of starting.

This is an ALH pump swapped into an AHU.

So far we've done the following:

Primed the pump and filter multiple times with a mitghty vac, also pressurized the tank, we had good fuel out of the lines, both feed and return.

Cranked the engine with the injectors cracked and all we get are dribbles of fuel and air bubbles.

Replaced the 109 relay

Checked wiring

Replaced the shut off solenoid with a used known good one

I then thought the seals on the pump might be bad from sitting, although there are no visible leaks. So we started replacing the seals, the old ones seem suspect, so I'm hoping that was the cause of the air in the system.

While we had the pump apart I realized the fuel adjustment collar was sticking, I'm used to them moving freely, this one was almost stuck to the shaft, I had to manual free it up. Then I tried manual cycling the quantity adjuster in the top of the pump, it would barely move. I have another old pump pulled apart and the springs cause it to snap back, this one at first was stuck in position and after sea foam now resets slowly but does not move easily.

Any suggestions for freeing this up? I think to disassemble the pump further to clean the shaft I need to desolder the connections, something I'm not sure I want to do.

There were also some fine metal filings stuck to the top cover of the pump. Not a good sign
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
Did you jumper IP fuel shut off solenoid directly to 12+v and try to start it that way?

The problem with diagnosing this one is that so many things were altered at the same time it makes it hard to figure out. It never ran after the rebuild so then messing around with the IP complicated it.

If the directly powered IP won't get it started I'd look for another IP to swap in that's either freshly resealed or known good used. You'll still have issues but the based on your description of the issues with your existing IP the chances are better that you would get it running.

Steve
 

lugnutgmc

Well-known member
Joined
Apr 12, 2013
Location
Rhode Island
TDI
Working on TDI swap into Mk1
So my biggest issue turned out to be a over restrictive and clogged fuel filter. I installed a Nicktane fuel filter with the 1 micron element as part of the swap. After sitting for a year I guess it was plugged solid. Bypassing the filter gets me good fuel flow to the injectors, and an almost start. Now I think I just need to dial in the timing. I remember when I installed the timing belt I had to skip ahead or back a tooth in the injection pump to be able to get the timing in spec.
Once I do that I think I'll be ok.
We also took the entire top of the pump apart and swapped good parts out from another pump to make one (hopefully good) pump.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
Having similar problems myself, did you ever get to the bottom of this? solenoid i can hear opening if i put 12v direct to it, plenty of fuel in the pump & filter, fresh fuel, new tank. Only getting the tiniest dribble out through the injectors after cranking for ages.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
Having similar problems myself, did you ever get to the bottom of this? solenoid i can hear opening if i put 12v direct to it, plenty of fuel in the pump & filter, fresh fuel, new tank. Only getting the tiniest dribble out through the injectors after cranking for ages.
Did you make sure that the ip harness is plugged in, both of them? Had the same issue, facepalmed when I saw the harness not connected all the way!
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
i hadnt but i did today and it was, seemed to pull more fuel through after changing the crank position sensor, but then i think i shorted out the cutoff solenoid haha! so im gonna try find one of them now
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
Sometimes better to start a new thread since the OP determined his filter was the problem.

Anyhoo, you should give some background. Was it running before? Did you change something, etc. Preferably in a new thread.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
i have ordered a filter for today so fingers crossed, i have no idea if it was ever running as one of its previous owners done the engine swap. I have had it start on easy start however so i would imagine compression etc is good. i will try the filter, if not i will strt a new thread and see what comes of it. thank you all for your help
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
If its plugged in, the shutoff got 12v and your not getting fuel out of the lines, you have broken wires in the harness. Very common at this stage
Check the wire harness very carefully for cracks or breaks on each wire all the way to the ECU from the IP.
Also make sure the harness and all grounding connections are good. If the harness plug at the head is not grounded it will do this.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
If its plugged in, the shutoff got 12v and your not getting fuel out of the lines, you have broken wires in the harness. Very common at this stage
Check the wire harness very carefully for cracks or breaks on each wire all the way to the ECU from the IP.
Also make sure the harness and all grounding connections are good. If the harness plug at the head is not grounded it will do this.
thanks very much for that, ill take a look at that when i next go over there! maybe worth getting someone in worst case to find wiring issues
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
It sounds like a lot of work but the harness isnt that difficult to get to. See the big round harness connection at the trans side of the head? Make sure its grounding eye is connected to the head and not corroded.
I've pulled the harness apart, took about 1 hour total to check it and another 30 minutes to put it back. Check the pins on the ECU to the IP.
A few members around my area had this issue and this was the problem I helpt out with. Most common area is at the trans bend next to the starter.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
It sounds like a lot of work but the harness isnt that difficult to get to. See the big round harness connection at the trans side of the head? Make sure its grounding eye is connected to the head and not corroded.
I've pulled the harness apart, took about 1 hour total to check it and another 30 minutes to put it back. Check the pins on the ECU to the IP.
A few members around my area had this issue and this was the problem I helpt out with. Most common area is at the trans bend next to the starter.
Is that the little spade connector towards the front of that bracket? i have noticed some blue residue on that so perhaps thats the problem!
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
Ok, tried all the above except checking the wiring so far. Installed a new fuel filter and nothing. I also installed a new fuel line as the clear pipe had a few hairline cracks and some tape over it (which filled me with confidence!)

However upon googling and trying to figure things out, I realise I replaced like for like, and it looks like the filter may have been installed back to front originally 😂 can anyone confirm if this would cause me these sort of issues? Is there a valve inside the filter stopping the fuel getting through?
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
I swapped the inlet and outlet on the filter once. It would start for a bit and die. Repeatedly.

Cause is the engine pulling air off the top of the housing rather than through the outlet pipe that has a tube that goes down to the bottom.

Could be your problem if you're sure it's right now.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
I swapped the inlet and outlet on the filter once. It would start for a bit and die. Repeatedly.

Cause is the engine pulling air off the top of the housing rather than through the outlet pipe that has a tube that goes down to the bottom.

Could be your problem if you're sure it's right now.
At this point I'm not sure about anything, a friend said about checking the pump timing or something. I don't know anymore 😭
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
Check your wireing dude.
I'm telling you.

Rule everything out. Put a bottle of diesel strait to the ip.
Harnesses connected
12v to the shutoff from battery
That right there will send fuel though the IPs head and into the injectors.
However, if the wiring harness is busted, like the wire wire for example that mark6 had broken, it will not start. Too bad you dont have vcds. You could check to see if the plunger is sweeping. That would tell you if the ECU is actually talking with the IPs QA
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
How could it be wiring when he said he had the hoses on the filter switched?

Fix what is known to be wrong, then chase wiring.

Good idea about running it off a bottle, though.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
I thought he said he suspects it could have been because its unknown and asked for clarification.
Also their are check valves at the tank.
Also I did not think it was possible to hook up a stock filter backwards unless the lines had been swapped wrong. I though this ran previously so I thought this isnt the issue. Now he is asking about timing and it's clear that somone who knows these cars needs to see it to diagnose what's wrong.
Hope OP figures it out but it might be a huddle gremlin, like the wiring.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
So fuel lines were correct after all. Getting someone in to check out wiring tomorrow and see if I have an issue somewhere. If not then it has to be the pump surely?
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
Could try running it off a bottle as Mong suggested while you're waiting. Could fill it with Diesel Purge instead of fuel in case the pump is gummed up from sitting.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
Worth noting on the bottle seemed to have a lot coming through the return, so maybe like you say the bottom is gummed up and it's coming straight through the return instead?
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
Getting nothing at the injeflcfor lines and plenty back at the return means that the QA is not opening. This means its ECU or electrical commands or the harness.
The pump is extremely simple. Km not sure why you have not checked the wiring by now.
 

AHUjackcaddy

Member
Joined
Jan 12, 2021
Location
harlow essex
TDI
AHU 1.9TDI In a Mk1 Caddy
Getting nothing at the injeflcfor lines and plenty back at the return means that the QA is not opening. This means its ECU or electrical commands or the harness.
The pump is extremely simple. Km not sure why you have not checked the wiring by now.
I'm absolutely clueless with wiring that's why, this has been cut about a lot. I have a new loom in the post as of this morning. What is the QA?
 
Top